Not familiar with the UA tables but I would not use the 2e system in a 3e game for two reasons:
First, the multiple XP tables. They weren't really a problem prior to 3e, but trying to use them with 3e's multiclass rules would be a huge pain. Also, XP doesn't progress the same way in 3e as it did in earlier versions of the game.
Second, I prefer how the 3e system award less or no XP for weaker foes and more XP for tougher foes. With the old 2e system, 20th level characters can still get XP for killing 1st level kobolds, which is just wrong.
Personally, I'm thinking of scrapping XP for klills entirely in my game and awarding XPs like story awards or such. I think it would be fairly easy to do this in 3e since the number of XPs need to level is always PC Level x 1,000.