I have a 642ci on the console and a 502ci on the bow. The 642 is a nice unit and I have no complaints, the internal antenna never looses gps signal, the sonar is strong and the screen has plenty of resolution to show 1 foot contour lines on the 08 Navionics Premium card. Whatever you do don't get the 502 thinking you'll save some money, the 642 is well worth the extra $$$.