When it comes down to getting commissioned, there are certain requirements that you must meet for a particular branch to commission you..ie, Naval Science classes, calc, physics, history, and computer sci requirements...so if you want to be a Naval officer, you must make sure you meet the requirements for a commission in the Navy. I dont see why you can't also participate in AFROTC, if you're curious about it, but there will be huge issues with your daily/weekly schedule as it will fill up with committments to each branch. If you want my opinion, it would look ok if you try both out your freshman year but after that, you should stick with one. If you try to juggle both throughout your college time it would look poorly upon your ability to decide (Decisiveness is a leadersip trait!), your ability to manage time could only go so far and you may be "speading yourself too thinly", and your academics (which matter most in getting you commissioned) may not get the attention they require if you fully apply yourself to both services. If you want to be in the Navy, do NROTC.