I frequently use both types of screens (A mix at work, and one at home). I can say that, all things being equal, if you aren't doing any type of intensive image work, it doesn't really matter too greatly as long as the curvature of the normal CRT isn't too great.
It also depends on the quality of the flat screen, expecially in the corners. I've used some 17" ViewSonic stuff (a75f or something), and the corners have fairly poor color covergence, and the optical trick to get a flat image was quite noticable as it was a bit uneven, eliminating any practical reason for a flat screen. Of course, my current new Mitsubishi 22" 2060u is an aboslute joy for my eyes since I have to stare at these things for hours
So, for generic stuff, including moderate gaming, I'd go with the more immersive 19", rather than a flat 17". If you need a high quality image more than size, smaller monitors at higher prices tend to do better. But do look at them both first, or failing that, at least get opinions on the specific models you are looking at. The final judge will have to by your own eyes.