Its not completely about what works, its about what works and doesn't give the client any toehold for complaints. Sort of like ammo. I basically never hunt with factory ammo, but a loaner would be getting nothing but premium factory with a known designer bullet. Otherwise, one way or the other every miss, every poor hit and any lost animal will be turned into my fault. Pass the guy lots of gun, storebought ammo loaded with bullets that nobody can really argue about, and a scope that nobody would confuse with a bargain brand and from that moment on whatever happens is on him.