For ultimate grip, the plate diff (gripper) is better.
For road manners the Quailfe is better, it doesn't clunk like the gripper, but it's not adjustable.
The plate diff on the road with circa 200bhp means you need to be a comitted driver- roundabouts in 3rd are awesome, and the level of corner speed you can carry with the throttle in is alarming! However the steering gets heavier and I would reccomend a subframe with them (and uprated driveshaft).
Gripper best for traction, quiff better to live with on a road based car.
I also have an uprated driveshaft, and obviously subframes if you need.
Cheers
Pete