my advice is to wait a bit until gen5 will be out. gen5 ergonomics are much better and closer to SF without backstrips. it handles much better than gen4.
Unless the grooves bother him and he needs an ambi release Gen5 is not even worth fussing over, frankly.
ETA: and I say that as someone who, as of right now, has 5 Gen5 pistols and likes them, but if they didnt exist I would have had Gen4s in that role, easily....