The Triton 400 has a lot of negative press. I've been using one without any problems though.
It was originally shipped with poor (in my opinion) firmware that Magellan has since upgraded. I don't think the current firmware is as mature as most Garmin products tend to be.
It comes with a very basic basemap with its newest firmware. The basemap has the state highways in my area but not much more. The Adventure Pack bundle that you can buy comes with National Geographic's TOPO! software. It has good 1:24K topo maps with it. I haven't yet found a source of free street maps so I'm delving into making some for myself. Magellan also sells street map packages.
I'm happy with the Triton but if you don't have time or inclination to play around with software I would go for the Garmin. Playing with the softare and maps are part of the hobby for me.