One issue I've seen with the Alpha is manufacturing inconsistencies. There is a significant difference in output sometimes between one motor and another. The GT's don't get anything special under the hood though. Maybe he got a 'bad' one or you got a 'good' one. I'm not sure if it's IM casting roughness or what, but cars that should be pretty much the same speed can vary by a lot. My Accent GT is about as much faster as you describe than my friend's base model LC2. I have big heavy wheels, a sub box in the back, power d/l and windows, and he's stock and doesn't even have a rear wiper, so ultra light. His car is way slower than mine for no real reason. I should also mention though that I have been beaten by stock base models though.
Does your friend have heavy wheels? I know those slowed me down.