If you can do both, by all means do both. You will learn a ton doing 121 time you just don't get in the Mil. You'll become much more familiar with the FARs, and going in and out of major airports will be eyeopening vs. the everything comes to a stop when you land at XX AFB. The more PIC turbine time you can pad the better as well as opposed to Regional SIC. Regional is good, Mil PIC is better, both is BEST!!

Best of luck whatever you do. I hope you catch the beginning of the wave that's coming.

P.S. Start stashing away savings if you haven't for that wonderful "probie" salary