I was once in your shoes, comparing polymer pistol brands on durability etc. The one feature of the M&P that swayed me away from S&W line was the trigger. I'm not sure if S&W improved upon it, but I couldn't get used to it. Other than that, the pistol felt reliable and durable enough to other polymer pistols within its price range.
I would not compare it in quality and function to an HK, though.