Sure none of them are perfect and they do all let you down from time to time, but the Satloc would have to be the pick IMHO.
Press the pattern button till you get to the pattern you want, press the wpt key (if you are in the right route) till you find the waypoint you want etc etc, they seem to just have a logical way of operating them.
The Agnav is the pits (if you are used to Satloc anyhow) having to find "F" keys by feel in the dark, with a piece of cloth over the screen because you can't dim it enough to stop blinding yourself, the lightbar is too bright for nightwork, and the angle lights work opposite to Satloc.
Agnav seems to be designed by computer nerds, though the firenav system looks interesting with a datalink between aircraft, looks much like a virtual radar with each aircrafts position mapped on your screen incl. their previous drops.
Forgot to ask what you think of the new style Satloc light bar?