How many simultaneous inputs will you need? If you only need two, the Mbox is great. I had one for a while and was pleased with it. The mic pres are good (for the price). Also, these days you get some goodies whenever you buy PT (Ableton Live, Reason, etc.). If you need more inputs, the Digi 002 Rack is great for around $1,200.
Another (HUGE) point to consider is ease of learning. Digidesign has tons of information for beginners, videos, free dvds, occasional free local seminars, monthly tips, etc. I've had difficulty trying to find info on Nuendo and others.
Pro Tools has my vote. It's universal, you can take your sessions to just about any other studio (if you ever have the need). That's the good thing about working with the industry standard.
Check out the free version of Pro Tools and some of their tutorials online.
p.s. No, I don't work for Digidesign. Hehe. I've just been using PT for quite a while and have been really happy with them.