I drove 2 Supersports within days of each other - 1 side exhaust - 1 rear.
IMHO the rear ones felt slightly quieter - especially when under heavy load. The side exhausts transported you from a road car to a LeMans GT racer. They impose themselves on the driving experience very strongly.
If you like big, bad, loud V8 sounding race cars - then go for the side exhausts.
If you will be doing a lot of long drives then you may find the rear ones a little more civilized.
