Quoted: The LED lights certainly don't have filaments to break. They are far more durable and have significantly longer lifespans. There are not many reviews or feedbacks regarding how well they work as weapon-mounted lights though. Al

The statement above is a big part of why most of us dont talk up the LED's yet.  The LED itself is certianly tougher and longer lasting but it's still too early to say for certain how well the circuitry side of LED's will hold up under repeated abuse.

As far as performance is concerned, for CQB use both lights will do a great job.  The M6 LED will give an excellent softer beam that's easier on your NV while the 6P will offer a bit more flood and longer range.  The M6 LED will taper off in performance better than a P60 lamp and it will have a longer runtime but you'll be locked into that performance.  The G2/6P series will have the capabilty of being upgraded to a high output lamp for even stronger performance (but reduced runtime) or even converted to a 9v system.

Quoted: I was mostly referring to the beams they produce (or the 'full-spectrum' intense light  they don't produce) rather than the electronics.

That's another great point though, an LED will fade (be less visible to the human eye) dramatically with ambient light.  For clearing buildings or areas where even a dimly lit street light is you can find the LED lacking.