I have been playing about a year seriously and used niether, although all my frineds use one or the other or both. I started using a gps on my phone, gloflogix, for $20.00 a year, pplus dat acharges. I have a generous data plan, use it mostly for golf. I got it because of a blind shot where I walked to the crest of a hill where I could see the top of the flag. Decieded to go left of the falg, stay away from the club house. Hit the right club, went right where I wanted it. What I didn't see by just finding the top of the flag, was water was to the left. Went in the drink, pin deep!
After about 4 months of using the gps, tracks all kinds of stuff, most of which I don't use, too time consuming. I noticed I wanted to start doing layout type shots. In case where I can't carry the bunker, water etc, so I got a cheap range finder. NO bells or whistles. Basic Bushnell. Used it for about two months, gave it a friends son who plays in tourneys. Upgraded to a Bushnell that does all kind of stuff. Love it! Especially when they have moved stuff around or the gps has the old course data. My GPS has given some really inaccurate data on some less than stellar courses.
I don't use either one every shot. Let's be honest..on a ggod day I carry the ball with my driver 225 - 240, on a bad day, well you know. If I am on a par 5, 580 yds, I know it is my driver, then my 3 wood, then I figure out what distance is left. Only way I use either one is if I am shotting blind (over a hill, dog leg, etc) or I am pretty close to the pin, let's say <200 yds. anything over is pretty straight forward.
I like them both, for different reasons. I would not buy a dedicated GPS, have too crap in my bag now, like the range finder for exactly distances, but really 90% or better, I use eye or course markers, and of course the score card. What I really need is buy something that puts some consistanc in my swing, imporves these old eyes finding the ball. then I will give up both!
Have fun with it, that's my two strokes worth.