Pitching up and down drastically will actually hurt the sound. There is only so much processing you can do. For regular tracks the up and down max is about 5%. Some sampling machines use midi sounds where this is not an issue as you can just tell it to play at any give speed. Anything audio based will suffer. WAV maybe a little less than MP3 (one less conversion to do), but still.
Personally I don’t think there would be a difference between speeding up a loop or starting a sample at a higher speed. The issue is pitch control. Switch it off and you can manipulate the speed as much as you want without too much problems. BUT … you will be going from Barry White to The Chipmunks as you slow down or speed up, which isn’t the intended effect I am guessing.
When you use the pitch control, the software will have to recalculate the key and that takes processing power. If the difference from the original key becomes too big, artifacts and unwanted harmonics will start getting in the way, not to mention processor stress might occur.
I am not that big on using loops/samples in my DJ-ing sets, so can’t be much more help there.
Greetinx.
.
