What branch should I choose upon getting commissioned?

Well, never forget that the Infantry adds color to what would otherwise be a bland affair.

Joshua, I don't have all the answers maybe a few suggestions form a semi broken warrior who has be were you are. It does not matter if you are doing 20 years or 4 years if you are not where you should be it will not be a good time. I went to Infantry IOBC/IOAC but I went to SFAS as LT and they did not have a SF OBC/OAC. I will say I knew when I made the jump I was right where I was supposed to be. I have a good friend who went Aviation and he flew several different birds he was right where he was supposed to be as well. Search your soul or being, research the branches, don't worry about making CPT if you do your job to the best of your ability it will happen.

I would definitely talk to an officer you trust will tell you the truth. If you really want aviation, talk to an aviation officer to see what the career path, growth, and promotion potential is like. I recommend you do the same with any other branch you're interested in. In the ARNG, there may be limitations on positions you can move into to promote. This can also be further strained by the amount of officers in your branch and in your peer group.

If you go to OCS as active duty you likely won't have the luxury of just chosing what to branch into. That's a reserve and nasty girl thing

I agree with CPT Campos above. You really need to find a mentor that is a commissioned officer aviator. Many of the ones I have known actually struggled a great deal because you just don't fly as often as you need to. The Army requires all officers to do those KD jobs like platoon leader, S3 planner, company commander, etc and your missions in those jobs do not include flying so I have had friends who struggled to get their flight hours. I know three people who actually went warrant later to just fly. In regard to alternate branches, look at what you're good at. If you are a god physically who longs for constant adventure and numerous deployments, go infantry. If you have a heavy STEM background, go combat engineer, etc. And yes, find people who have served in those areas to help you. Also, as a fellow OCS grad, I can tell you that on branching day you will not have as much power as you think to pick your branch. They will put the branches on a board with the numbers next to them as to how many slots are available for your class. They then call you up in class standing order to pick your branch. So it behooves you to do the best you can in OCS. In my class, infantry, armor, and MI went first and by the end about the last 50 in the class had their pick of transportation, ordnance, and chemical. Just to give you an idea of what gets picked first and left to last.

Thing might have changed but if I recall whent it was time for commissioning - regardless of the source - you had a prioritized which list and the army took care of the rest based on its need. Nevertheless the odds of getting one of your top 3s was high! Know wit regards to which branch... Is all about what you wan to accomplish and availability; as a NG you might be limited.

Military police pretty well needed in both the active Army and both the Army National Guard and the Army Reserve. I don't know the trends but you should check in the Army times and see. Your retention NCO should tell you where they are needed. One suggestion I make is that once you make it to Captain and you've completed your Captain's career course I would suggest going into some secondary functional area like civil Affairs because those people are always needed and your skill-set from whatever Branch you choose plus maybe even your civilian job will help there. I had no problem making Major having civil affairs under my belt. I have never been active duty but with my deployments I have three mobilizations and a total of three Battle Stars. You also have the opportunity to be in the active Guard Reserve which is you would be part of a battalion or Brigade Cadre that keeps the unit going in between unit training assemblies and they get the same exact benefits as active duty as well as to active duty schools. There are boards held annually for positions available Nationwide. If you are active Guard Reserve in a reserve unit you also get full basic allowance for housing and moving expenses just like the active duty.

SPC, Go Aviation for as much as you can. I was too old by the time I went to OCS for that so I went Infantry. A lot of fun, but not much practical value post military. ....and that day eventually arrives. Logistics, Intelligence, SF, lead to rewarding careers after your 20. I went Civil Affairs and that helped too. Tip of the spear is exciting, but as I am finding out now, support services have more career opportunities in retirement. I am getting by on my leadership skills, but a specific skillset would have made my job search easier.
Any way.....I envy your position to be entering OCS and starting an officer career.... I would do it all over again if given the option. Good for you, good luck! If you go combat arms, go to Ranger school. Tabs go a long way. One regret I have was not taking that road when I could have. In the 90s, there wasn't any emphasis on it in my state national guard.

Aviation was my first choice too. I was assigned to IN/MI and every good thing that happened or I experienced was in IN. My buddies who went AV said that flying time gets few and far between after CPT. The heart of the Army is IN and the only thing I would ever recommend enlisted or commissioned.

I would have gone AV for sure, but didn't qualify during the physical. Now I'm MI branch detailed to IN (which I volunteered for). I think its the best way to get small unit leadership experience as an LT, then go on to more broad picture things later on as a CPT and up.