This won't tell the whole story but it should give you a good idea of how it compares to your pistol.
Unload your M&P.
Get a piece of string and a ruler. Loop the string around the trigger and around the backstrap of the gun. Let it go where it wants in terms of where it settles on the curve of the backstrap and on the curve of the trigger. Don't pull it tight enough to stretch the string or move the trigger, but take up all the slack in the string.
Measure how much string it takes to make the complete loop.
When I measured my CZ-75, the string required to make the loop was 7.4 inches long.
For comparison, the same technique on a Gen 2 Glock 17 resulted in a length of 6.9 inches.