Dots are certainly more versatile, can more explicitly define a tune, can be applied to other instruments, there's more music available, and it helps you play with a wider variety of other players. Reading dots also imparts an informal, unconscious understanding of scales and theory that I don't think tab really does for most people.

However, tab can be a quick and dirty way to pick up a tune, because you CAN count frets to figure it out, without mucking about with the key signature and is-that-a-half-step-or-a-whole-step. Then some folks just think better with a picture. And for some folks, I think tab helps them make the tune their own because they HAVE to guess at some of the phrasing.

But guitar tab only works on a guitar, and if you're playing the mandolin you have to find different tab for THAT.

If you are comfortable reading the dots, count your blessings. The best of options seems to be to learn both, and I think tab will make more sense to you as your skills develop. I think dots -> tab is a much easier learning transition for most than tab -> dots.