I would agree the G5 would be better, maybe not worth the extra $20 unless you are a pretty serious gamer. The adjustable resolution, and how easy it is to switch, plus the extra forward navigation button is really nice. (I kinda am picky about this small detail... )
*EDIT* If you're looking for a good overview of the difference, look at the last page of that review.
i have the MX and i love it its perfect for the serious gamer and or the internet user the foward and back bottons are very helpful i never downloaded the software so idk anything about the software