Which centaur is more 'official'?

Question

I've got a player in my campaign and she's an equestrian, so naturally she likes centaur characters! She wished to use the centaur character race from Unearthed Arcana (UA), but I realize that there is a similar race described in Guildmasters' Guide to Ravnica (GGR) which has subtle differences (like damage dealt by the hooves and charge distance).

I only wish to use the one that's officially supported by Wizards of the Coast, so which one should I use - UA or GGR? If both are officially supported, which is more popular?

Answer 1

This is answered directly by the box text at the beginning of every single Unearthed Arcana article:

This Is Playtest Content

The material here is presented for playtesting and to spark your imagination. These game mechanics are in draft form, usable in your campaign but not refined by final game design and editing. They aren’t officially part of the game and aren’t permitted in D&D Adventurers League events.

If we decide to make this material official, it will be refined based on your feedback, and then it will appear in a D&D book.

Anything in Unearthed Arcana is pre-release playtest content that might be finalized later in an actual book, adjusted and rebalanced based on the playtesting and feedback that came from UA. Only the book version is "official". So if both exist, the printed version is the "real" version that you should use.

In this case, the centaur and minotaur in the Centaurs and Minotaurs UA were playtest versions of the two races before they were actually published in GGtR.