Nobody else can make this decision for you - do your own research (if you go for a degree it will be good practice) but go much deeper than you have tickled so far.
The Military route will be the most secure - at the moment and is probably quite safe at least up to the 22-year point. I believe Pension Rules will change soon (And probably certain to be brought in as part of signing on?)and that could have some sway in your decision.
In civil life you have to have at least one year on the outside "with" your licence sitting in your pocket (if you have done the modules before leaving?) to have any hope of making a similar amount.
Staying in too long may mean that you could work for very little without an immediate pension to support your new career.....
Just my opinion...
Best of Luck