I have a 60CSX and love most of it, apart from the electronic compass which is a waste of power and money. Go for the Cx model and save money!

I haven't tried a 76 so can only make limited comments:
the 76 floats (although the 60 claims to be waterproof and is certainly rainproof),
the controls for the 76 are at the top not the bottom (personal preference?),
the 60's external antenna will probably work better in poor signal conditions (otherwise why bother make it external),
Garmin seem to update the 60 software before the 76 for similar upgrades (maybe the 60 sells more)?