This all came up recently at the NFL combine because Cal's QB Jared Goff could be the first quarterback drafted in April and there were concerns before he measured up with nine-inch hands. This might have been specific to Goff because he notably was benched during a 2013 game (sheets of rain were coming down) because he couldn't hold onto the football. So having big hands that grip a football probably helps avoid fumbles and it might even help with QB accuracy.
But it doesn't help with the other 99 things a quarterback has to do like read defenses, checkdown receivers at the right times, audibles, leadership, etc. etc., so it isn't a sign that someone is going to be great just because he has meat hooks. But it also looks like you can't have average size hands and expect to be a starting NFL quarterback.
NFL QB hand size chart for those wanting to compare while you’re supposed to be working pic.twitter.com/C4ug6Ra3kG— Busted Coverage (@bustedcoverage) February 25, 2016