Another vote for the Montana. For years I've used the Montana 600, from back when Garmin first introduced this model. Never had a problem with it, despite several crashes with it mounted on the handlebars of my dirt bike and my quad.
Garmin just introduced the Montana 700 series, a major upgrade. Come Black Friday I'll be investing in the Montana 750i - because that model incorporate the InReach technology right into the GPS unit. That will allow me to stop paying for expensive air time on my satellite phone and use the InReach texting capability instead, a cheaper alternative.
Keep in mind, if you do go for a Garmin outdoor unit like the Montana, unless the model number has a "t" in it, it will NOT have maps on it - that surprises a lot of people. If the model number has the "t" in it, that means it has the Garmin 100k mapset of the entire United States already loaded on it. But - you can also load your choice of maps onto a micro-SD card and use them also - the unit will allow you to select which mapset you want. A lot of the guys use hunting maps which are very detailed. Any number of places will allow you to download free maps - check out gpsfiledepot.com for some good ones.
Because my eyes are very old and very weak, I loaded the Garmin 100k maps onto my automotive style GPS unit - that 7" screen is wonderful. Never would have known there was a "Boobs" Canyon to explore if I hadn't seen it on my screen:
For off-highway use though, an automotive-type unit is very limited. You need the capability to create your own tracks to follow and then load them onto the GPS unit and only a handheld/outdoor type Garmin GPS like the Montana allows that.
This is a shot of the screen of my Montana 600. The data fields on the right can be removed - or you have about 50 different parameters you can have displayed there. The red line was a track I created to follow and it is overwritten with the cyan line the GPS created when I actually rode the track.