The 798 replaced the 797. I had a couple of the 797's. If my memory is correct the 797 only had one card slot for maps. The 798 has two slots. One for a map card and one to record images and information. I went from the 797 to the 998 because of the larger screen. My eye sight isnt what it once was and the larger screen is a big help. If you get a 700 series HB use a RAM mount to mount it to the boat. The base unit is weak and during cold weather if you just grab the unit and try to tilt it you will break the base down near the ratchet. I broke two of them. No problem after I used the ram mount. I used the ram mount to move the screen. Hope this helps.
