While I do enjoy Darkness Falls I do think it's gone too far in the "difficult means bullet sponge" direction. Or maybe black hole rather than sponge. You can progress to get OP weapons to fight the seriously OP monsters but then all the normal zombies you find become like gnats buzzing around your face. Just an annoyance rather than something to be concerned with. Undead Legacy has not gone there yet, at least not that I know of. I haven't played the latest updates, waiting for the 2.6 release. If it's the "grind" that you think is difficult, both are rather grindy but you do feel a sense of real progression rather than just grind for grind's sake.
No? Well, at the current time Undead Legacy has no bullet sponge enemies so to speak. The only new NPC he added is a scorpion but it's killable with the current weapons and tools. No gimmicks like Darkness Fall's supernatural creatures.