Like norm, I have both. 90% of the time I use the 800, when I know the weather is going to suck, I take the 705. This was a result of the SSAP in which my 800 became caked in mud...buttons stopped working and it eventually just stopped working completely. Thus im a little suspect of its abilty to take the punishment the 705 can. My 705 has survived skiing, snowmobiling, motocross, biking, jogging, mud, downpours of rain, you name it. Its a very tough. The 800 is nicer. Maps are better, more screens, and ability to swipe from screen to screen. While the features of the 705 and 800 are almost the same, the 800 just all around works better and the mount is night and day better.