You can run more inputs on the profire+ it's a better interface (DSP mixer is a huge thumbs up to me).
I say m powered. I have no idea why it would be considered the lowest pro tools. Having gone from LE to m powered I can tell you first hand LE and M powered are identical out of the box (well.... except the icon).
I don't agree with the cubase sentiment either (and cubase what I primarily use, I'm not a giant pro tools fan), software is just how you work not how you sound.
Yeah lack of ATC is kind of a bastard, but there is a way around that.
I understand wanting pro tools while at school, it's what they teach therefore it's what you will want to use.