I use both. I have a Garmin Nuvi 2455, and also a Droid Turbo loaded with OsmAnd. I prefer the Garmin, but it's not one of those "it has to be a dedicated GPS system or else you suck" type of preferences.
The Garmin is easier to see in the daylight than my phone. The Garmin screen is pressure sensitive, rather than inductive like my phone. Makes it easier to push a button on the GPS screen with gloves on (though I did sew conductive thread into the index fingers of my gloves so I could activate the cell phone screen).
I use the Tyre program to create routes. It's easy to load routes from Tyre onto both the GPS and the phone (OsmAnd will read a .gpx file created on Tyre and give you turn by turn directions just like a GPS will). The upside to using the phone is I can create a route on Tyre and email it to my phone, then open it in OsmAnd; no usb cable needed.
I still use a GPS, for much the same reason that some guys will wear a pair of boots long after their usable life span is ended; because it's comfortable to me. In the past I've bought used and refurbished Garmins on Amazon for a very decent price, but I've noticed lately that their used prices have increased to the point that they're now in the range of a used cell phone. My next GPS will be a an old smart phone. I'm not going to activate it; I'll just use the built in GPS and download a offline maps program like OsmAnd, or maybe Co-Pilot. I need to do additional research for an offline navigation app that can accept a premade downloaded .gpx file and can provide turn by turn directions. OsmAnd does fine with it, but I've never really grown to like it.