It depends on what you want to get while in the military. These are my experiences, and I don't mean to slight anyone by the below, but here is my take on the 4 main branches:
The USMC is the tops when it comes to discipline, toughness and personal pride. They are last in equipment and facilities, though. Great deployment locations, and lots of travel. Every Marine is a soldier (sorry, but there's no other term) first. (They hate being called soldiers, but saying they are Marines first doesn't get the point across.)
The USA is great for leadership and managerial development for both enlisted and officer. Their locations tend to be the worst, though, but that is where all the money is going since they are getting all the press in the current war. (It changes from war-to-war because the USAF got all the money for a while after Desert Storm).
The USN has awesome base locations, and lots of travel. This is the branch where you will get the most technical training. Bases are very spartan because their money goes in their ships.
The USAF has decent locations for bases and the best base accommodations. This is where the high tech toys go most often, but the chances of getting to take them out for a spin is the lowest, since there are not as many operators in the USAF as there are in the other branches. This is the most civilian-like of the branches, too.
If you need any help, I'd be happy to assist. I always recommend going to college first, if you can, since you get more pay/benefits as an officer. But, the hurdle is paying for college. You're not too old to win a scholarship, though.
I can help, especially with ROTC and OTS, since I went through both.
One note, the gender barrier has been mostly broken in the USAF. We have several female aircraft commanders in my squadron, and several radar navigators (these are the two leadership positions on our 5-person aircraft...I am a radar navigator).
I have loved the USAF since I joined. I went through USA ROTC at a military school, but I decided not to commission since I would be sent to armor if I didn't make med school in my first try (I didn't). So, I tried to get in for 4 years and then started talking to the USA and USAF. The USAF said I could fly, so here I am. God has really blessed me in my work. I have had opportunities that were unbeknownst to me before I joined. They are even paying for my Masters of Divinity (seminary degree). I have done well in my career field and I enjoy flying a lot. I have not seen combat, but our platform is relatively safe when it is employed. This was a reason I asked for this airframe. I've gotten my first choice in each of my assignments.
God bless you,
Capt Dave, USAF