Montana 6xx can´t use any of the following nüvi 3790 'features' files with current firmware:
- No 3D buildings with ***3D.img files.
- No Junction View with JCV files.
- No Enhanced Pedestrian Mode with cityXplorer maps containing MMR data with public transportation routing. cityXplorer maps is just like ordinary pedestrian mode in City Navigator when used in a Montana unit.
- No Automatic Speech Recognition with ASR-files & SXR-file.
- No trafficTrends™ or myTrends™ features with G2S-files and DB-files.
On the other hand you can use BlueChart g2 (even g2 Vision but without showing the Vision extras) with correct marine colors. The only nüvi´s that can show marine BlueChart maps correctly are nüvi 500 & nüvi 550. TOPO maps shows like all other premium outdoor handhelds and geocaching is rather well implemented.
The benefits with Montana are more based on the profiles and the maps you enable and disable for each profile. Enable marine BlueChart g2 maps for the Marine profile and disable TOPO and road maps etc.
The variety of customisation features and possibility to doing that for different profiles are really good and the major strength of the Garmin Montana series. The weakest feature would be the "nüvi" road navigation profile if that´s compared to a nüvi 3790.