IMO, it is waaayyy to early to think about dedicating your life to a particular FFP. It would not be surprising if you choose one this year, only to find that next year another is better for you, not to mention there will be a totally different environment when you finally finish school. Even now, your desirable "least expensive flights" and "large network" don't necessarily go hand in hand.

By all means stick with DL in the short run if you think that works for you. Hang out here, learn more about this and the other FFPs, and when you are ready to really fly the friendly skies regularly, then find what works for you at that time.

Oh, and welcome to FlyerTalk!