Aside from the chance to interview with United, there is no advantage to Aviate and UA does not give any preferential hiring to partner companies. In fact, the major downside to Aviate is that it's one-and-done. Fail the interview and UA will never give you another chance, through Aviate or off-the-street.

Do not go to any UA partner regional for Aviate. There was some advantage to the program it replaced (known as the CPP) as compared to off-the-street hires, in that the entire interview was a 45 minute session of "story time". Now, however, everyone in Aviate does the same interview as an off-the-street hire.

The success rate for Aviate is reportedly around 30-35%. That's either working exactly as planned or is failing miserably at its task -- I don't know which, but I'm sure someone in UA does. My guess is, as most people on the thread covering this subject have surmised, that Aviate is nothing more than a recruiting tool designed to staff the regionals -- not UA per se. I've flown with my share of guys who have passed and failed the Aviate interview and it's clear they're leaving some very good people on the table, so I'd call that a "fail", regardless of the intent of the program.

Since you're still in school, my advice is to keep doing your research, as this industry can turn on a dime. The "preferred" regionals of today may very well change in as little as six months so I wouldn't lock myself into any particular program or regional at this time. Just keep your eye to the sky, so to speak, and apply to the most appropriate place(s) when you're ready.