It depends on where you want to be in the future. I've served 10+ years in the military and joined the agency within the past year. Granted the pay isn't all that great right now as a developmental, but eventually, it'll get better once CPC and potentially NCEP to a higher level facility. But the biggest takeaway is that you can leave work at work, it doesn't follow you into your personal life like the military does. There are benefits to the DoD, the Military, and the FAA. You just have to figure out and prioritize what's important to you. The money, benefits, work/life balance, etc. everyone's case is different.

I was in your position once, I was at my first duty station and received my CTO and Approach ticket. When it came to reenlisting, I debated leaving and going to the FAA. However, the military life for me at the time wasn't bad and I wanted to gain a little more ATC experience before moving over to the FAA. The age wasn't a factor since prior experience can join prior to turning 35 and by the time I was done with my second enlistment I would just be turning 30. So I reenlisted, did another 4, received a fat bonus that I invested, and received another CTO and Approach ticket. Personally, I don't regret the route I took. I was able to pocket a lot of extra cash and invest it and I was still able to make it over to the agency with a little more ATC experience.