Carnifexes: Bonded Exoskeleton or Extended Carapace
The Carnifex has a base 6 toughness and a 3+ armor save. Is it better to increase their toughness to 7 for 20 points or to increase their save to a 2+ for 25 points? Most people I think go with extended carapace. Personally I don't want to do both so that I can keep my 'fexes a little leaner.
Extended Carapace - Against things that don't ignore it, a 2+ save vs a 3+ save means that you have half the chance to fail an armor save. This means a greater resistance to small arms fire, high strength poor AP weaponry like autocannons, and infantry assaults. It also gives you a save vs. AP 3 weaponry of which there tends not to be a great deal, and gives the fex a little help against snipers. The downside is that you are wasting points when getting shot at by lascannons, melta weapons, or anything else that ignores/penetrates your armor save.
Bonded Exoskeleton - The extra toughness gives you greater resistance to everything that the extended carapace does except AP 3 weaponry. In addition, it also gives greater resistance to things that do penetrate armor like power fists, monstrous creatures, and melta weapons. The downside is that it does nothing against str 4 weaponry or str 9+ weaponry, which still wound on a 6+ and 2+ respectively, and it also does nothing against sniper weapons. It also makes the fex immune to str 3 weaponry, not that that will come up often.
At first I favored the extended carapace but then I got to thinking and I think I may like the bonded exoskeleton more. Neither helps any against lascannons or railguns, but I think that the bonded exoskeleton will help in more situations, though when it does help it's often not as dramatic as the extended carapace which halves the probability of failing the armor save.
So what are your thoughts?