I have an o7 and rode the 07 Gixxer 1000(same exact bike as 08), and what's funny is, they feel like they have almost the same powerband, it will go to the rider....
as far as looks go, the R1 looks way better, and the 07 R1 has more power than the 04-06 R1 as does the Gixxer to the previous one, especially on top...
the brakes and suspension stock for stock are wayyy better on the R1...I can guarantee that, tell your bro to watch his forkseals, they are a bitch on the gixx 1000s...even without wheelies