SP- difference at the top end could be 2mph. (The difference when spinning a 53/12 at 100rpm compared to 50/12 at 100 rpm is 2mph.) That's huge in a race.

For me, as a recreational rider, it's more important for me to be comfortable climbing. As a racer, it's probably more important to be able to go fast at all times!

For what it's worth, I have two bikes with compacts - one has a compact-specific FD and one has a standard FD. I can't tell the difference - they shift just fine. And, it's probably not ideal, but I swap my 12/26 and my 13/27 without changing chain length or RD.