Yeah they do tend to be pricey. I had a Sigma 40 before this M&P. It was all over the target.
This M&P is the most straight shooting compact I have ever shot.
I'm not too crazy about Poly either but for the concealed carry, this is perfect.
I would go with the 3rd gen if these are your only choices.
You mentioned that you wanted a 40. take a look at the M&P 40c. This is what I carry in the summer months. If you go this way call S&W and request the pinky extension. It is worth it.