Pitching Wedge: It's better to have a straight leading edge when you need to belly the ball onto the green. __Sand Wedge:__The curved leading edge gives you less margin for error on this short-game shot.
If you like to play bellied wedge shots when the ball is against the collar of the green, as I do, I suggest a pitching wedge rather than a sand wedge. The leading edge of a pitching wedge is straighter than the curved leading edge of a sand wedge. Your chances of aiming accurately, making clean contact and getting a true roll are better with the straighter-edged pitching wedge. I even grind my pitching wedge to make the edge truly straight.
I treat the bellied wedge like a putt. I use my putting grip, ball position and stroke to hit the ball in the equator. Versatile wedge play like this is becoming more and more prevalent in the modern game, with refinements in equipment and technique. Phil Mickelson is known to carry four wedges for a wide variety ofshots. I've always recommended that average golfers have three wedges, dropping a long iron. I even added a third wedge recently.
I find myself in the position of needing a 52-degree gap wedge more than a 2-iron on Champions Tour courses. My other wedges are still a 47-degree pitching wedge and a 58-degree sand wedge.I hit my sand wedge 95 yards and my pitching wedge 125.
Before I added a gap wedge, I would manipulate a pitching wedge for shots in that 30-yard gap. That worked when I was practicing and playing more, but now the gap wedge enables me to hit those shots with a normal swing.