There is someone on the local web selling a second hand MX300.

Is the MX300's sensor a lot lot better than the G1's that I should just leave the will to buy the brand-new-in-box G1 to buy that second hand MX300?

Cuz actually I don't like it to be second. I'm more into buying things new cuz I like them to be flawless-no stretchmark, clean and fresh. The G1's seller also provides a 1-year official warranty.

I want to use it to play Counter-Strike 1.6 where I have to aim and control the recoil of the guns precisely.

And no, none of my friends have those mice so I can't test them.