I recommend Golfshot GPS as the best app for on-course usage. I compared the distances between my SkyCaddie and Golfshot and most of the time it was the same. At most it was 3 yards off between the two devices. It works so well that I cancelled the SkyCaddie. Since it is such a battery drain you should use it with a battery case or something to give it extra battery power for a full round of 18 holes.
Also, it lets you keep score and stats on your round that you can review at a later time.