Using a pattern board positioned 40 yards distance - shooting the same gun with two shells, one loaded 1100 fps the other loaded 1200 fps - which will have the larger dia. pattern. Guesstimet as to how much larger.
With the same choke, they should be the same size. The lower velocity shell might shoot a tad lower, but should be the same size. With a full choke you should have 75-85% of your shot in a 30 inch circle.
I tend to disagree that the slower velocity load will have the 'same pattern percentage or fundamental density throughout the pattern.
All things equal (powder type, wad, shot hardness, barrel choke and forcing cones - my experience gives the slower/ower pressure load a slight advantage presumably due to slightly less shot deformation - and thereore 'flyers'.
Whatever opinion you want however, ou should be able to get one.
My only recommendation is to try 'em under controlled conditions, including recording velocities - and counting pellets...