My buddy put on one his boat this spring. At first I thought the only difference between it and my 787 was the screen. Mine is 640 x 480 and the 788 is 640 x 640. Same resolution, I think, just a wider screen. I like the 788 better. It also has two card slots as opposed to the one in the 787.

As far as the unit itself, we have not had a problem with it at all.