As stated there are distinct differences in paths based on where you are on your way to completing your degree requirements. If you have more than 2 years left to complete your BA/BS the ROTC(regardless of Service) route may suit you best. If not, wait until you get your degree and apply for the OCS/OTS route. One thing to keep in mind: Accessions by source vary amongst the services. Simply stated, ROTC/Academy grads sometimes have more aviation slots than OCS/OTS grads. This is done for a few reasons that really dont concern you at this level, but will impact your ability to garner a slot should that be your desire. Historically I think it has been easier to walk in the door of OCS/OTS with an aviation slot in hand(done through the recruiting process, but still competitive) rather than compete at the ROTC level. At the ROTC level you are not just competing with members of your individual unit but rather with members of all the units in your 'year group' or commissioning group. Bottom line is you have options, you just need to research your options. One final piece of advice - Don't put all your eggs in one basket with one service. If your desire is to serve your country first, fly second, keep the press on and find your niche, the rest will work itself out in time, flying or not.

Good luck