I put together some metamorphs yesterday (strictly rule of cool, model-wise), but it brought me back to something I've thought about before - rending claws vs metamorph talons.
In terms of acolytes against metamorphs, the points now heavily favour acolytes. But what if you've decided to put down some metamorphs anyway? How should you arm them if you're looking to get the most out of them?
Options and Attacks
Metamorphs come with three options - rending claw and talon, pair of talons, metamorph claw. The metamorph claw offers strength, the talon hits on 2s, and the rending claw can trigger AP-4. So which comes out on top? In considering this, I've also taken into account the number of attacks associated with each: the metamorph claw hits hardest, but because you sacrifice the talon to gain it, it only has 3 attacks; the rending claw also has 3 attacks, but gets a bonus attack from the talon; and a pair of talons gets you up to 5 attacks.
Rending Claw or Metamorph Talon?
So, first things first. Because the basic metamorph comes with both rending claw and talon, we need to know which is more useful in any given situation. And it turns out to be pretty simple. Against a model with a 6+ save (or no save at all), the talon out-performs the rending claw (because the +1 to hit is more useful than rending); against a 5+ save or better, the rending claw is always better. For a basic metamorph, then, they should use the rending claw as much as possible, unless fighting against 6+ saves, in which case using the talon for all four attacks is a better play.
In a head-to-head comparison, we're pitting the four attacks of the basic metamorph against the five of the paired talons metamorph. We'll optimise those attacks, so the basic morph will use his talon for 6+ saves, but the claw the rest of the time.
And the outcome here is, again, surprisingly straight forward. Five attacks with talons is the better option against anything with a 4+ save or worse. Three attacks with a rending claw, plus the bonus talon attack, produces better results against a 3+ save or better. The toughness of the target has no effect on the decision - all that matters is the save. If we expect to face power armour, keep the rending claw; against anything lighter than that, the extra attack of the paired talons tips the scales.
[For completeness, given that a talons morph is 15 points and a basic is 13, I also worked out the point efficiency. Turns out that talon morphs are more efficient per point against 6+ saves, basic morphs are more efficient against 3+ or better, and they're exactly even for 5+ and 4+. In short, if we choose the more effective choice, we'll also be picking the more point efficient one too. Simples.]
What about the Metamorph Claw?
Well, it's a thing. The metamorph claw, even at only three attacks, is the most effective option against T5 and T8 targets (T5 is the comparative sweet spot where the rending claw and talon wound on 5s, but the metamorph claw is still on 3s; and T8 sees the other options drop to wounding on 6s with the metamorph claw still on 5s). And on a 14 point model, it's also the most cost effective choice against those specific targets. So if you're facing off against an army of T5 and T8 models, load up on claws, I guess.
So it all turns out to be pretty simple. Against 4+ saves or worse, go talons; otherwise, stick with the rending claw; unless you're just going to be punching T5/8, in which case break out the metamorph claws.
I generally run my Cult as Twisted Helix, which means I gain +1 strength, making the metamorphs a base S5, and the metamorph claws S7. This has no effect on the balance between the different options - talons are still better for 4+ or worse, rending claws for 3+ or better. The metamorph claw now shines against T6 (rather than T5), but loses out overall as S5 models don't drop to 6s to wound until T10, and you don't see a lot of that around.