M&P Question-Barrel Length

[sherwood49]

While at the LGS yesterday I noticed that they had a M&P Item # 206301. It stated on the box that the barrel was
4 1/8". My brother has a box that states his is 4 1/4" Which is right?
I'm torn between the one with a 4 1/4" or a 5" barrel.

 

[OKFC05]

Don't know about your box, but S&W says the nominal barrel length is 4.25

SKU #: 206301 Caliber: 9mm Capacity: 17 Rounds Barrel Length: 4.25"
M&P9 - 9mm - Smith & Wesson

As to the barrel length preference, I bought both the 9mm Pros: 5" with FO sights and the 4.25" with night sights.
The difference I notice most is that the 4.25" barrel is comfortable in a Safariland ALS holster while sitting in a vehicle, and the 5" is just a bit too long to sit comfortably.
I use the 5" FO version for IDPA and USPSA, and the 4.25" for everything else.

 

[Wee Hooker]

The shield has a 3 1/8" bbl. The double stck M&P's have 3 1/2 , 4 1/4 and 5" .
Owning all three of the double stackers, I can tell you that there isn't a whole lot of measurable accuracy difference at normal shooting ranges. Buy what makes you happy and what meets your needs.