well, I'll try and comment on this. There are going to be trade offs either way obviously. I went v7 207 because this car is my primary and daily driver. the swap took a little more than a day to do. I did not want to deal with the downtime. THe OEM build is just sweet. I didn't want to deal with the issues inherint to built motors since I put alot of miles on my car. capt said it. its soooo smooth. like, scary smooth at 8k, it feels like the motor isn't even trying. I have a green right now with avcs not working (I know, its just been spiting me). I would have NO issues going to a 30R with avcs and w/i.
that all beign said, a 2.5 that could rev to 8 ALL DAY LONG without oiling issues would be the ultimate, but in order to find something that could reliably do that, we're talking big $$. v7s do real well in stock form. the motor just runs quiet, it purrs.
in all, I would only go 2.5 if I could afford to do it right, make the car spin to 8, and have a powerband that would hold up there.
I wouldn't do anything different, honestly. I'm very happy with my setup.