Note - I've been using civilian GPS for as long as it has existed. My first couple units didn't even have rudimentary mapping - they simply reported a position that then had to be plotted onto a paper map to be useful. Which is why I'm still a die hard UTM user and hate lat/lon to this very day... But I've been using them a long time and have owned quite a few units.
I've also owned and used "smart phones" and played with the various gps and mapping apps for as long as they have existed. As well as, at one time, it was literally my job to obtain every single tablet and Oragami device that hit the market and test out various GPS/Mapping apps on them for the company I work for. Note though, that tablet experience is several years old now so no longer relevant.
Anyway...
I find that one of the features I appreciate most about a dedicated GPS unit is the dedicated buttons on it for dedicated features. Trying to manage waypoints, tracks, zoom, look up POI's etc. on my phone is a total PIA compared to the same tasks on my GPS units.
But, there is a tremendous amount of personal preference to be accounted for in the above. Like, for instance, I prefer GPS units with actual buttons over touch screen units. For two reasons. One, I find the dedicated function buttons far, FAR easier to use while bombing down a rough dirt road at speed. And second, and this is PURE personal preference, but I HATE the way touch screens are always a greasy dust attracting smeared oily ugly looking mess. I think display tech has improved to where touch screens are the equal of non touch in terms of being readable in sunlight, but for the generation of GPS units I own, that was a HUGE deal too - the backlit non touch screens were (are?) just way better in varied lighting conditions.
Again, personal preferences, but I also don't like trying to make one GPS do it all. If it is small enough to be useful on a hike, I think it totally sucks azz for screen and/or button size in a vehicle. I like bigger displays in the vehicle. And I like something totally submersible and built to take a lot of bouncing and vibration. That's why I use a marine chart plotting GPS in my vehicles. It's actually made to go on a boat. The one I have now is an old model that I'm sure is discontinued, a Garmin 276C. But if I were buying a new one today I'd get whatever the newer replacement model for it is.
Oh, and the most important feature of all, really, is the cartography available. I have not researched it recently, but as of a year or two ago, Garmin cartography was still light years better than what was available for Lowrance, for my purposes. Otherwise, I'd have bought one of the Lowrance Baja HDS units - they totally rock in every other feature category I'm concerned with. But, if the maps suck, then what's the point and at the time I was looking, the Lowrance maps DID suck, royally...
So, distill it all down, my personal preference for in vehicle use is a Garmin marine chart plotter
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- DAA