But depends on many factors a ml with high Km well cared for may be better then one with low Km and not cared for.
So a lot is up to the prior owner.
As to power yes that it has. Ability to over take that it does. Do We like our 03 ML500 had it for 2 months, and no regrets.
But if you have something go wrong can you do the repairs yourself that will save a lot of money if you have a budget.
Look here for common ml issues