Yeah, I'm a Cubase user as well.

I actually started back in 1991 using Opcode Vision, which was almost identical to Cubase.
Then I went to Cubase 2.5... eventually upgraded to Cubase VST 24, then finally right now to Cubase 4.

What can I say.... I used to have major problems with Cubase customer service in Canada (Ray Williams, the old Canadian rep was extremely rude to me on the phone when I called for support and for some reason he now runs the Canadian company).

Their tech support has greatly improved however and they've been very helpful in sorting out some initial bugs.

Anyways, to answer your question. I've never used ProTools really.
I attempted to use the free version of ProTools Light a few years ago but found it overly confusing and not very intuitive.

Cubase has a steep learning curve if you've never used recording software before but there are some excellent DVD video tutorials from ASK Video that get you up and running in no time.

And what can I say.... I use it exclusively and the ability to time stretch and transpose audio files on the fly is majorly convenient.
(Like seriously... it's like every audio, midi or rex file is completely fluid and you have total freedom to adjust audio files to fit your songs.)

Just as a fer instance, I needed a keyboard riff to add to one of my songs from a sample recording that was originally at 120bpm in the key of A.
Just a couple of clicks and I slowed the track down to 100bpm, transposed it to E and matched it up with the original song. And you can't hear the difference at all.

Anyways, personally I'm sticking with Cubase. I've used it now since about 1992 and come up with some decent recordings even on ancient Mac equipment going back 12 years. (in fact my entire 2nd album was recorded on a Mac G3 with only 512MB of Ram and the songs are still getting picked up for TV commercials and movies.)