The game mechanics work quite well together, you can run in guns blazing, it will work, but you won't come out unharmed(IE, quicker but more risky. You can also decide to go stealth, which requires more planning, takes more time, but if it works, you can finish a mission with a "perfect" score. In short, I think the game rewards you in the right way for the effort put in.
Edit: To avoid double-posting: