Well, I'm not saying the Sentra is junk, but I personally would get the Corolla over the Sentra because:
1) The resale value is much better, so when you leave home and want to get that Maxima you really want, you won't have to pay as much for it
2) It gets better fuel economy; again, you can save more money for your Maxima when you move out
3) Historically, it's one of, if not the most reliable vehicle model ever; less likely to spend $$$ on repairs, more $$$ for Maxima in future
4) If you're not getting the car you really want now, might as well get the one that's going to get you to the car you really want sooner ...