IMO, it is always best to slip. If you rev it up, and drop it, physics comes in to play. Lets say you drop it, get good grip...The front end will rise very quickly and then drop, and when it drops...it WILL slow the car (no matter how high the drop is). this is why when top fuel dragsters go, they have those things on the back. Not only will they flip over...but they will be slower if they did not flip.
Lets say you slip. Rev to 5 grand drop halfway or so, and then slip it out. You will have continued power and you will launch your self out. I have seen MANY people try the dumping thing, and they will never get as good 60's IMO. Not to mention dumping it, you may snap **** (as did i).