White T-shirt guy,
I've used the G3 and I liked it. Was probably the biggest skimmer I've owned. It was on a 65g + 20g sump system. So I guess it did more than fine for the amount of water I had in there. My fish bioload was on the low side though, I only had 5 or 6 fish and they were all on the smaller side.
The g3 should be fine, but if money and space allows you could go with the g4.
I notice though that they raised the prices on the ASM's, the g3's like $310 now and when i bought it, it was like $230 ish. You friend might want to look into another brand skimmer for that money. Could probably get something more well built, becasue mine used to leak around the joints. Just a though though.
-krisEN