Tony,
After shooting an IDPA night shoot last month, and finding my mini-mag light horribly inadequate, I borrowed the match director's Surefire G2. WOW! Huge difference. I realize your question was about the difference between two Surefires, but I'm of the belief that more light is better, and I recommend the G2. I've since gotten a G2 Combat, and will be using it Saturday night at the next IDPA night match.
Yes, the G2 only has 20 minutes of light per 2 Surefire batteries, so my solution is to always carry extra batteries. You can buy a box of about 12 at surefire.com for around $17. And, for situations where I would need light for more than 20 minutes, that would usually be in the car, so I left my mini-mag in my Explorer.
The G2 Combat is also very light in weight.