I have a Bushell 4200 Elite on my ML. Nice scope, clear and lifetime warranty. I also know a number of people who use the Bushnell 3200 on their ML or rifles and like them. IMO one of the best scopes in their price range. BTW, a 50MM objective will give you about 2% more light gathering capabilities than 40MM. So you decide, if that is worth the extra cost.

Whatever scope you choose, match it up with some good solid mounts and rings, I would look at the leupold or the likes, Quick Releases. Makes cleaning the ML a lot easier.