The first difference you'll notice on the well-named Wide Sole irons is the extreme width of the sole. This is designed to let the club head glide across the turf and helps high handicappers who tend to hit the ball fat--or strike the ground slightly behind the ball.
Unlike the pro level, high-performance wedges Callaway designs for highly skilled players, the Approach Wedge is made more like a typical iron and takes advantage of all the game-improvement technology available, from perimeter weighting to wide sole to cast steel and multiple material design. The 51-degree model is a gap wedge that fits well between the standard pitching wedge and higher-lofted sand wedge.
Most high-level wedges are not designed using perimeter weighting technology. The wide sole Approach Wedge, however, is. This enables the average player to take advantage of all the top-tier capabilities of Callaway and still utilize the game improvement component of cavity-backed perimeter iron weighting.
With top players like Phil Mikelson on staff, Callaway is tuned into the needs of the lefthanded player more than most golf equipment manufacturers. The classic challenge for lefties has always been finding the same clubs a company makes for righthanders, but in lefthanded models. Luckily, Callaway makes all its Wide Sole Irons for lefties.