I'll put in a vote here for rail tape as a newbie paddler.
I'm glad I put it on our Tufskin Starboard SUPs, when we were just beginning and falling off, and whacking the board a lot. Now I'm not so sure we need it as much.
The rail tape does show some gouges and nicks, that did not translate into chips and cracks. Plus the Tufskin seems to get dirty if you even look at it funny. Perhaps the biggest use for the rail tape is the ability to put the board on it's side (leaned up against a car/pole/fence on the pavement while dressing/undressing/ loading. I'm sure it's prevented lots of nicks. I also feel better knowing that I can stack the boards on their side on the pavement in my driveway without hurting them.
Rail tape might be advisable if it's a recreation board that's used by your kids/dogs/neighbors, etc. Not everyone will treat your board as well as you do.
That said, I don't have rail tape or a paddle guard on my race board. Nor will I have rail tape on my new 9'3" subvector.