I've never used protools before and I've never used acid pro to record. I do, however, use acid pro to slice together my sound files and layer them when making songs. Acid makes doing this very easy, which I like a lot. But since I've not tried them both, I can't really comment on which is better.
I use acid - great, great, great program if you're working with loops, and it's a pretty intuitive interface. But, pro tools takes this one simply because acid only allows you to record a single track at a time.
Yeah Acid Pro is not really comparable to ProTools, different sort of program. Acid Pro is a loop based program (well last time I used it anyway, my copy isn't the most up to date). ProTools is a multi-track recording program.
At the risk of sounding contentious, I would be tempted to say that Acid Pro is not a serious studio recording application, and as such cannot be compared to Protools in any meaningful way. A better poll might be Acid Pro vs Reason or something like that.
It CAN be used as such - I've been doing it for a while - but it's primary focus isn't recording audio input, but rather working with audio already on a system. As such, it's great at what it does, but like I said, it can only record a single track at a time, and that;s a MAJOR limitation for a studio program.
I have always used Acid. I have tried others but I always end-up coming back to it. Its just a case of getting used to a certain piece of software, but I really like this one. I havnt tried protools as of yet.