I switched my GPS for my smart phone full time for the last 5+ years. I've never looked back.
Google Maps is just getting better and better, with almost unlimited POIs that are up to date with good reviews. The turn by turn routing is the best of any device I've tried, and it even has lane directions, telling you which lane to get in to make the turn. This is really hand for RV drivers. It'll route you around traffic and construction.
I find it *so* much easier and faster to look up addresses or destinations on my smart phone. GPS units seem clunky in comparison. If I really want to see where I'm going, I can even turn on satellite view or look at streetview, showing me exactly what to expect when I get somewhere. This is a big plus for an RV driver. This ability doesn't exist in stand alone GPS units.
One of the biggest things missing for me when comparing my smartphone to GPS, was a "search along route" functionality. Guess what, Google just added that!
Smart phone car mounts are even easier to find than GPS car mounts, and have more variety, so no problems there.
Going somewhere remote? No problem, you can use Google Maps's offline feature to download maps before you get there and store them on your phone so you don't need to use data.
Planning a trip? Use Google Map Maker to mark the stops you want to go on your computer at home. It'll automatically show up on your phone.
What if I break or lose my phone? Well, as a certified geek, I always care a spare phone. But, even without that, my co-pilot has a smartphone as well.
With all that said, if you like using your GPS unit more than your smartphone, awesome! RVing is about the different sorts of people I meet. If we all liked the same thing, it'd be boring.
