I've used the Montana on my Moto for years both as an auto-routing GPS and a track following GPS. I've even used it hiking a few times but I do find it a bit larger to carry around. I did need to fix the battery-reboot problem of the Montana by placing a foam earplug in the battery compartment
Before that it was the Zumo 500, Oregon, the 276, GPS II and one that that only displayed Lat/Log and a directional pointer.
When the Overlander came out I had a Montana and a RV routing GPS. I decided to sell both of those as the Overlander provided the same capability in a single unit. Today, I've used the Overlander in RV mode while driving my class A, in car mode while driving the Jeep on highway and in the Offroad mode (tracks) while driving the Jeep Offroad. I have yet to find a limitation to the Overlander in any of these modes. It handles routes or tracks. I also download the satellite imagery while Offroad to aid in campsite selection. I've loading tracks onto the Overlander while in the middle of nowhere with zero cell phone reception. I've also downloaded tracks in the middle of nowhere and loaded those onto the Overlander via the web based explorer site when I've had cell phone reception. After the first two software updates the Overlander has become stable with added functionality (The Montana needed a few updates too). Actually, the Overlander always functioned well as a GPS. It was just the update process that wiped out some of the downloaded POIs that needed to be fixed.
While I've not acutely tried loading a track into the Overlander via the SD card (new capability in the last release) I did see the option. I'll give that a try in the next week or two just to make sure it works. Before that it was possible to load a track into the Overlander but you needed a computer that had access to the Overlander file structure.