Id go the small turbo if 300 bhp is enough. It suited me better and they seem to drive much better and has a much smoother power delivery in my opinion. Ive heard a few say that a 300 bhp ST is faster than a 300 bhp LT upto about 100 mph. I also found that the small turbo's seem to be lower mileage and most that I viewed seemed to be more looked after and less abused than most of the big turbo models, although obviously thats not always the case but seemed like that with the cars I looked at.

Its all down to personal choice at the end of the day though mate.

Just dont buy the first you see and youve got to drive a few of each, big and small turbo, then all will become easier to decide one way or the other.