Reaper here. Also an audio engineer. Also have a (fully paid up) copy of sonar producer 7, that I choose to use reaper over.
I keep thinking about getting PT10 (when it was PT9 and all of a sudden I could use my RME and Focusrite interfaces with it), but the only real draw to me is easier collaberation with other studios/engineers etc.
Last time I used cubase is was SX3, so I'm quite out of date now on steinberg, but it was good, I liked it.
Given reapers power and efficiency, theres really no reason not to try it. At all.
Ben, I have to question the comment that cubase 'sounds better' than PT. All DAWs audio sounds identical: as good as your DACs, or more likely your room and monitors. You should know that mate ;). Unless you mean the on board effects are good, in which case, yes, they are/were good last I checked. Better than PT, I cant say. I tend to use voxengo, stillwell, cakewalk (will load in anything VST-using if sonar is installed), slate, etc etc.
Aside from anything else, if youre new to the DAW world, then its best to start with whatevers most readily available, since capabilities of DAWs tend to differ in often quite peripheral features. The basic cabilities of tracking, editing, comping, effect treatment, automation, tempo mapping, time-shifting, midi programming, routing, bussing etc etc etc are all there in each, and I feel that its more valuable for a first time user to learn these capabilities in whatevers comes easiest to hand (or comes easiest to the wallet), while trying to get time on as many as possible and making your choice based on your preference of how one does certain things over another, rather than what one can do that another cant. Most of your time is going to be spent doing certain main activities, which will vary depending on how you intend to work and what you intend to record, and getting something that does them in a fashion you agree with is more important than getting something that has some snazzy feature you like the look of but only use once every 6 moths.
To make that decision effectively as a neophyte, you can cut your teeth on any of them, just to learn what to look for in all of them.
For example, I can use superior drummer 2 (which I often do) in either sonar or reaper. I much prefer how reaper does it. The result is the same, the quality is the same, the capabilities are very nearly the same, the difference is the process (part of whats often called 'workflow' and is really a very big deal).
