Cool edit pro and ACID really have a different background.

Cool edit started as a shareware audio editor. When the pro version came out, they added multitracking in it. Now they developped it so far that Cool Edit Pro is on par with softs like Wavelab and Samplitude.

Acid was really made as a "loop" multitracker. It has a powerful algorithm that can match BPM of your loops to the BPM of the master track, and so you can easily construct your own song. They have developped that algorithm so it got better and better. Effects (like directx and VST support) came second.

So my question is, what is the main aim of the program? Will you record the vocals/whatever else and process them, and later use them in a sequencer (Cubase, Logic, stuff like that). Then I think Cooledit pro is the way to go, as it is still aimed at audio editing.

If you want it to be integrated in a loop based environment, ACID is the way to go.

For cooledit you have good alternatives with Wavelab and Samplitude (they are more expensive, but more pro oriented also).

Acid still is one of the only softs that makes and handles ACIDised loops (so they can be BPM adapted). But there is quite a good (more powerful, but more work for you) alternative with Recycle (a slicer). Several progs accept recycled samples...