I know a few guys with 8ightEs (running the losi esc/motor) and they love it. I also know a few guys with 8ights they converted w/ mmms and they love it.

From what I can gather the MMM is a lot more customizable and (as long as it doesn't fail right out of the box) a lot more dependable.
Based on user accounts the MMM seems to be more forgiving then the losi system for those not as experienced (at racing).