My D24 business coupe has a 3 spd with fluid drive. It is definitely not fast. I have not driven a D24 or P15 with a regular clutch set-up so I really can't say how they compare. I usually start off the line in second gear and it is OK for normal driving. (first gear is very low, probably good for mud or steep hills) It is possible to start off the line in third, but when I do, little kids on tricycles complain that I don't get out of the way fast enough. Once rolling it is very easy to drive and when the fluid coupling is fully engaged, around 20 mph and up, I wouldn't think it would make any difference. It is also very easy on the clutch. When starting out my procedure is 1) depress the clutch and shift into second, 2) release the clutch but hold the car with the brake, 3) release the break and accelerate away. 4) at around 15-25 mph depress the clutch to shift to third. The clutch is not slipped at all.
Dave