My M&P .40 uses two different holsters....my IWB is a Milt Sparks VM-2 and my OWB holster is a Kramer open top that was originally for a Glock 22. The price was really right (free). Both have served me VERY well. My advice is buy the best Quality holster with the features that you like. Again a good quality holster from most any of the major manufacturers will serve nicely. Get a good quality belt as well and you will be a happy camper.
Randy