You can make a good go of it in any of the armed forces - but you *have* to be self-motivated. Don't know about your armed forces, but when I signed up for the U.S. Navy, I got my technical schooling (avionics) "guaranteed" to me as a condition of my enlistment. I needed good scores on the entrance tests, and the "guarantee" is really only "best effort" - so don't go in thinking the government is legally bound to give you a certain set of training. If they want you to peel potatoes, well, you'll be up to your ears in spuds. However, a good can-do attitude will take you a very long way indeed.
You have to understand that there is a remarkable amount of bureaucratic bullshit in any military branch. Your ability to to carry out the bullshit without bad attitude or insubordination is directly linked to your advancement and placement. In fact, if you demonstrate ample proficiency in whatever task you're given (no matter how trivial or demeaning!), you may find yourself in a position to change things if you go about it the right way - but always remember the chain of command. Never skip it.
Also: understand this: You are at the service of the government. Don't sign up unless you understand what that means.
None of this is meant to scare you off - I had a great 4 years, and I'd do it all over again in a heartbeat. I got to go places I'd never heard of, do things I never imagined, and was given responsibility hard to imagine as a teenager. Plus, I got lots of good stories and bullshit to tell now ;D