The closer, tighter grip results in better purchase for your fingers, resulting in a more effective grip overall which I believe lets you control the arc a little better.
I also believe the beavertail spreads the pounding from recoil on the web of your hand, decreasing pain and fatigue in a longer (or shorter, more violent) shooting session. Go ahead, do 100 rounds with a Colt Commander with a "pigtail" safety in 1/2 an hour and I think you'll see what I mean.
Thanks, Xavier; well done.
Cheers, TF