The third difference will likely require the use of a good handgun scope and good bench rest shooting technique. Because your M&P R8 is capable of shooting sub 1 inch groups at 100 yards with the right ammunition. BAck when it was first released Guns and Ammo tested the R8 wtith a scope at 50 yards from a rest and got sub 1/2 inch groups at 50 yards with a premium SD hollowpoint ammunition. I've also seen similar results from my model 620 with also features a tensioned barrel. The plain and simple truth is that tensioned barrels are more accurate than one piece barrels. However, if you are shooting offhand without optical assistance you'll probably never notice the difference in accuracy. Because it's quite rare for someone to shoot well enough offhand over iron sights to come even close to the accuracy a plain old 627 can produce with it's one piece barrel.