I chose location and it was the right choice for me and my family. There are a few more things you might want to think about.
Think about job security. With the BRACs that will be coming up, one base may have a much higher chance of being shut down than the other. Finding out how "safe" the bases are is the hard part.
What type of flying do the units do? Depending on the unit, the KC-135 may sit alert quite frequently which might be better for your situation than the C-17 which probably has longer trips. Or, you may prefer the longer trips.
Guard vs reserve makes a difference too. Especially if you might need to relocate in the future for an airline job or family obligations. From what I've heard, it's a lot easier to transfer between units within the reserve than the guard since each state has its own guard bureau.
Availability of pay days may factor into your decision. I don't know what your situation is, but you might want to have the ability to pick up extra days of pay (furlough, don't have another job, etc). Talk to both units and see how many days you can expect.
If you have an airline job or are thinking of getting one, distance to the closest airport and their flying schedule may make a difference. Obviously, commuting is gonna be easier or harder from different airports for different companies.
My point is, location and airframe aren't the only things you need to consider. You'll only know if you made the right decision after the fact though. Good luck with your decision.