B4i was specifically designed to combat KLs, when those were added to the game.
https://glb.warriorgeneral.com/game/forum_thread.pl?thread_id=5084141&page=1#47368111The value of AF% all depends on what your baseline is.
Like if you're a pHB with 90+ Strength/Carry, then AF% would be significant.
On a typical receiver, B4i will be better because it's a linear addition.
Stacking AF% on top of B4i would be the best option. (Ldo)
Don't bother chasing 0 KLs. There's significant RNG involved so that defenders based on KLs don't become irrelevant. Eventually a defender will roll well and you'll get KL'd.
Remember the offense is "penalized" if you want to think of it like that. They have to both Catch and then Hold On. The defense can just load up on KL enhancements.