I have the 788ci it will do everything the 798 will do beside's the side imaging. The pre loaded maps are just basic map's with about 15ft contour lines, very little detail. I just bought the navionic's premium map's east and it has alot of the local lakes in hi-def (nolin,rough,tville,barren,c-land,dale,kentucky,barkley,and I believe green and laurel). The gps is a must especially on a lake like kentucky and barkley, if not just for the safety factor of seeing the channel's, but it make's finding those ledges and ditches very easy. I wish i could have gotten the side imaging, it's awfully sweet, maybe the next one will be and can link them up.I'm very happy with mine so far.
Kydog