With the added options for different types of Power Weapons in the game they have become a lot more versatile, in many ways replacing the need for Fists and such due to simply being significantly cheaper. However, with an array of different choices picking one can be tough (at least for those who aren’t committed to one option due to a particular model.) However, I think there are some good guidelines for how to pick which one- and when to spring for something different- based on some general criteria.
The Power Sword
Good ol’ reliable. The Power Sword is still, most of the time, the same as it was before- 2+ saves are, for the most part, the exception on the field and many xenos armies can’t really field them at all. While you shouldn’t ignore the possibility completely, neither should it be dominating your thoughts when picking weapons, as it’s simply not something that is going to come up all that often.
The Sword will be a strong contender for weapons when your initiative is high enough for it to be relevant- if you’re less than four, don’t even bother worrying about it. 5+ is your golden number here, as it means you’re killing Marines before they can kill you, but even I4 models are at least guaranteed a chance to swing against most people. Of course, there is another caveat to that- you need to be worried about killing Marines. Some armies are; some aren’t, so it will depend on whether you have enough ways to handle heavy infantry already. Understand that this is a concern, as you are going to see more armies running significant numbers of bodies on the ground, so it’s important to be able to handle them, one way or another.
What a Sword won’t do for you is help against big targets like MCs or vehicles. While this isn’t a change from previously, the fact that there exist other options for doing so with your Power Weapon mean that you have to consider whether you’re going to need more help against them or in killing MEQs, which is a perfectly valid question, but one you need to consider.
The Power Axe
In some ways more similar to an old-style Power Weapon than the Sword is, the Axe will cleave through absolutely any kind of armor save the enemy might have. (Warning: guarantee not valid against invulnerable saves.) Not only that but you get a strength bump as well and, unlike its close relative the Power Fist, you can still benefit from having an extra CCW. Of course, like the Fist, you’ll end of striking at the bottom of the initiative order, which can sometimes be a bit punishing.
Axes are excellent when you can guarantee they’ll get their hits in, which can mean any of a couple different things. First, it can be on ICs where you have the ability to pawn off any wounds allocated to them with your LOS rolls. However, there is also a good possibility you’ll get involved in a challenge with an IC, so be sure you aren’t crippling yourself by striking at I1. The second way is by having a 2+ save yourself, which will largely ensure that no one who can punch through your armor gets to swing before you; there are of course a few rare weapons that do so and Monstrous Creatures will give you a bad day, but that was probably true anyways. Last but not least, you can simply have a horde of expendable bodies to soak up the enemy’s wounds, guaranteeing that you won’t need to even worry about making saves on the model with the Axe.
Axes, bizarrely, are probably the most flexible of the weapons and are well-suited to general use- if you’re not sure what else to take, consider taking an Axe. However, sergeants in particular should be wary of doing so lest they get challenged and die too easily. But for models like Terminators, Death Cult, etc, that all get to pick weapons, Axes are a great way to have utility against just about everything you fight.
The “just about” clause is worth remembering, though; an Axe isn’t really going to be much better than Krak Grenades against a tank and even against foes like Orks and Necrons will be wasting whatever Initiative value your model might have had. Anyone with I5+ should probably avoid Axes, as striking ahead of Marines is generally a big deal and shouldn’t be discarded casually. +1Str also means that, like the Sword, it is unlikely to do much damage to high-toughness targets like MCs unless you get lucky on the wound rolls.
The Power Maul
Sitting in an odd place in things, Power Mauls are weapons that don’t really mesh with the common assumption of a Power Weapon- that is, eliminating armored targets. Though it can punch through medium armor saves, it will do jack diddley to Marines and the like, so it’s generally pretty safe to assume that the enemy is gonna be ignoring 1/3 or more of your Power Maul hits. In compensation, however, you get a hefty +2Str and Concussive (a la the Thunder Hammer) as well as swinging at full normal initiative.
A Power Maul, then, is most useful against targets where your model’s normal Str value would be insufficient to do much damage; this generally means enemy Monstrous Creatures, against whom a Sword can generally cut through the armor but finds it difficult to actually score a wound, and against vehicles, where getting one S6 Krak Grenade attack ends up feeling a bit weak. Models with low natural strength, such as Eldar or Guardsmen, may find Mauls helpful in wounding the abundant T4 enemies, and on Marines S6 meets the Instant Death threshold for such weedy races when directing attacks back at them- and there’s something to be said for splattering a Farsser, Archon, or Company Commander in a single blow.
Thus in general a Maul will be your weapon of choice when you want to handle something significantly beefier than you are, no matter what race you may be. The add-on of Concussive isn’t a huge deal but will occasionally be useful, especially since it guarantees you get to swing before them again next turn. (Interesting note: If you are swinging before them with the Maul model anyways, Concussive will actually force TWO rounds of I1 swings on them, which can be relevant if other models on your side are a bit slower.)
The Maul’s big weakness is the one we brought up immediately: it doesn’t actually help you get through armor most of the time. Since that is more often than not the purpose of buying a Power Weapon, a Maul tends to be a somewhat specialist choice compared to the other two.
The Power Lance
A.K.A. the Bad One. While not completely worthless, the Lance suffers from not really doing anything particularly well and being reliant on the charge in order to get any real bonuses. When charging, it’s an upgraded version of the Sword, getting +1Str in addition to AP3. However, any other time it’s just a poor man’s Maul, lacking any bonuses except the weak AP4. In neither case does it have any special qualities, making it a rather weak contender.
For models with Hit and Run and an upgraded movement speed (like cavalry or bikes) the Lance can be a reasonable or even good alternative at times, since it allows you to get high-Str hits in at initiative and ignore most armors. However, it is still unable to penetrate Terminators even under its ideal circumstances and, lacking that specific combination of abilities- or should you roll poorly on your attacks or HnR test, it’s very possible you will be stuck in with a mediocre weapon trying to bonk enemies to death with a long stick.
When considering Power Weapons, Lances can effectively be discarded as an option except for very, very specific units. It’s probably fortunate that they have the most unusual modeling option correlated with them, as it would be fairly miserable to get stuck using one on most units.
Of course Power Weapons aren’t the only option for most models- Marines especially have several other similar options that tend to come on the same platforms and perform similar roles, so it’s worth taking a cursory look at these as well and establishing some guidelines as to when they might make the grade over some variety of Power Weapon.
Lightning Claws are so close to Power Swords in overall functionality as to be almost identical in most circumstances. The reroll to wound is almost perfectly balanced by missing out on an attack due to being a Specialist Weapon (since they virtually always come on A2 models with an extra CCW), with only slight advantages for one or the other on and off the charge. The Sword has a slight edge in having a higher maximum damage output and can kill T3 models better, and conversely the Claws are more reliable and better against T5+ enemies. For most squad leaders they are so close as to be basically a personal preference, though on someone with three or more base attacks the Claw ends up being a little bit better.
Power Fists are essentially like Power Axes, being able to kill just about anything effectively. Tanks, MCs, characters, whatever- they inflict Instant Death on most anything they’ll fight and consistently down 1-3 guys per turn. All of the same considerations for protecting the Axe are also applied here, but a Fist has a huge boon in being able to down all but the most resilient of challengers from a single failed save, which can often double or triple their effectiveness against an enemy IC. Nowadays you will mostly want to look to using Fists on ICs of your own that can keep themselves alive with good armor and invulnerable saves (rather than sarges, who can be challenged out), but their utility can make them a good choice for just about anyone.
Meltabombs are a cheap upgrade option for many characters that give you a way to smash vehicles (and, to a lesser degree, MCs) even when equipped with a low-strength weapon. If taking a Power Sword they can be a nice little addition to give you some extra flexibility when assaulting or being Tank Shocked.
Swords, Axes, and Mauls all have their place in different armies and different units, depending on the types of units you want them to be able to handle as well as the existing offensive and defensive abilities of the unit. Overall the change has added another interesting layer of decision-making to the game, which is a good thing for players of all stripes. While it may be annoying to remodel old characters in order to give them more edition-appropriate gear, I think it’s a small price to pay for a huge boost in flexibility.