As a drummer I have to stand down here and say... Electronic kits are bullshit. Point made. Thank you. If he's too silent he should either hit harder or get some mics to mic up his acoustic set. I've played E-sets... from cheap china crap to the high quality roland shit and have to say that they felt nothing like a real drumkit... the cymbals alone are worth vomiting.. no real feel... I played half an hour on an E set and my wrist started hurting... turns out the stupid drum pads are nothing like real drumheads.. who would've thought that.. shocker... I don't recommend electronic sets.
I agree with the above. your drummer should try using "bigger" drum sticks, just a suggestion not a definite solution.
Side note: One of my friends has an electronic drum kit (Roland). His house is small and cramped, so it works for him, and his parents are both musicians so they don't want to really hear drumming after a day of recording, lessons, etc. It's kinda fun to mess around with all of the different settings and for recording it's really easy, just plug it in to the interface. So in a lot of ways it can be nice, but it more ways than not, the practicality of an electronic drum set is a "lie."
No digital signal can truly convey the feel of a drum set, either being heard or played.