I have my yellow car with the Caterham 6 speed and the Orange car with the Sadev 6 speed sequential and the geartronix paddle shifter.
I can say that the Caterham 6 speed is equally at home on the street or the track. Easy to shift, clutch firm but communicative, very good all around. IMO
The Sadev in the other car, seems to be ALOT noisier, very quick on track, and with the flat up shift and Blipping on the down shift, it makes you feel like a driving god on the track. This car is set up with an extremely lightweight flywheel and a race clutch, which makes starting out a chore. The fact that you have to shift all the way up or down before getting to Neutral makes it a little less Street friendly IMO. I tend to think of this car more a track weapon than a street car. Now that may just be how the clutch and throttle are set up, but It is noisy, and harsh. Like I said, on track it is like butter if you just think about lifting on the upshift and the down shifts no longer require heel and toeing. Tom