Zero K is uglier but has a full campaign, more units, and is less micro intensive.

BAR has better graphics and tiers of units ala classic TA (zero K is flatter), and more active multiplayer.

They both have Total Annihilation as a distant ancestors.

As someone who played a lot of Warcraft 3 and really enjoyed the campaign before wow was announced, I was not pleased with the MMO announcement.

Aka “buy the rumor, sell the news”