9/10 times, the gun will outshoot the operator, so asking which is better largely depends on personal skill, adaptability to a specific firearm and other factors.
I don't know which one is more operator-friendly, but generally speaking, a good operator will transfer his skill over to any sidearm with little or no time needed for adaptation.
There's no such thing as your example of a good shooter on A, but terrible on B. I've seen complete newbies shoot a variety of handguns and their skill (or lack of, depending on the individual) was consistent across the board.
If you can shoot the Glock, odds are you'll adapt quickly enough to the S&W. That doesn't mean you'll be shooting bullseye right away, but you will be consistent in your grouping, and the rest will come with a bit of practice time.