Members, I am evaluating a couple of different weapon options and am trying to figure out if it is better to have a 1 better to wound, or a -1 rend? specifically, with all other stats the same the weapon statlines in question are: 4+/4+/-1/1 vs 4+/3+/-/1
It depends on the save value of the units are targeting. Against a unit with a 3+ the rend is better. Against a unit with a 5+ the extra to wound is better. Two additional things to consider: Some units who are under the affect of buffs to their saves, such as the one provided by the Lord Castellant, are greatly hampered by rend -1. Skeletons are everywhere in the meta. Rend -1 leaves them with only their Deathless minions save. You will almost double the number you kill by just having rend -1.
If not equal they are nearly indistinguishable. You always end up with a fraction for the value. So who knows which side it would favor in reality.
Ideally you can manage to pull out both, but faced with a choice I tend to go with rend. Edit: I can generally trust my own dice to carry me through the hit and wounds, and I find that messing with my opponents rolls can sometimes be more beneficial than buffing myself.
Another small thing to consider: If you know that you will face Nighthaunt on a regular basis, better go for damage. Rend doesn't work against them.
As a general rule: Rend is more effective the better your opponent's save is. +1 to wound is more effective the worse your base-value is. E.g. -1 rend has a larger relative effect going from 2+ to a 3+ (going from 1 in 6 failed saves to 1 in 3, doubling how many fail) than it'l have going from a 5+ to a 6+ (going from 4 in 6 to 5 in 6, only increasing the failed saves by only 25%) This leads to the following funny looking table: - Good save, Bad wound (e.g. 2+ save vs 5+ wound): both will give roughly equal improvements - Good save, Good wound: Rend will be more effective - Bad save, Bad Wound: +1 to wound will be more effective - Bad save, good wound: both will again have fairly equal results - Save and Wound both at 4+: both are equally valuable (assuming no re-rolls or other nonsense of course) Where a "good" would be 2+/3+, and bad is 5+/6+.