I was thinking about the 226 myself. Some are made in NH. when I was talking to the range master about the 226 and the M&P he said both were excelent handguns. The Sig was a great gun but the company itself definetly has room for improvement, the costumer service sucks. The range has to constenly replace the barrels on the guns because of so many rounds being fired through them. He said the Sig needs to have a new barrel every 200,000 rounds, as for the M&P need a new barrel every 400,000 to 600,000 rounds. The Sig need to be tuned up quite a bit more than the M&P. That is just for the amout of use they get. Its a try before you buy range.
Personally I believe the more gadgets are on a gun the more can go wrong with the gun. The M&P does not have a whole lot of parts and is very easy to disassemble completely and clean and the sig is more like taking apart a 1911 but with a few more parts. If anything goes wrong with the S&W the factory has a 2-3 week turn around and it has a lifetime warranty. They pay for any shipping both ways and will give you a couple extra mags for the trouble. If they are not able to fix your gun you get a new one. The Sig, you need to make prior arrangements with the shipping, pay for it, and get your own insurance. you may be lucky to get you gun back in 3-4 months, even at that they may not have solved any problems, just given it a shot.
Whe you shake an M&P there is a little rattle but how often to sit there and shake the gun. There are only 4 connection point of the M&P ant that minimizes the chance of dirt getting in there and making the gun malfunction.
When you do more research on the Sig, be sure to check the ammo you can use with the gun, cast, +p, +p+ etc. be sure the chamber is fully supported like the S&W. I say this because if its anything like a Glock you'll be in deep doo doo if its not.
I am buying the M&P .45 FS next week for a side arm when hunting and HD. I have large hands and my girl has very small hands. the M&P will accomidate us both. I plan on buying the Apex trigger for it to bring the trigger down to 4 lbs and that will lessen also as the gun gets used. If you were to take the trigger assembly and the sear assem. apart on the M&P and polish everything up real good you will not have the "gritty" trigger. You can also send it back to S&W and have them do it for you at no charge. They will send you a couple free mags too.
If I were you i would think about it a little more. I agree with most of these guys when they say save your money and get the sig aswell. I would not sell the M&P untill you have the Sig and have used it alot. There is a huge market for the M&P used. if you sell it yourself or put in on consignment at a GS you will not have a problem selling it later. I saw one guy at the local range wanting to put the M&P on consignment and before he could agree to the terms of the GS another individual offered to buy it from him for alot more than he would have gotten if he let the GS sell it for him. i hear this happens quite a bit with the M&P's. I see Sigs all the time there on the consignment rack, they sit there for quite a while. Sig also charges $139.00 to have a new buyer send it in and get it reconditioned. I think that may be a down fall on sigs part.