In terms of gameplay, Terran. They are the most straightforward and I find them to be fairly decent at the start game (disclaimer: have't played much of Starcraft 2 in general, most of my experience comes from the first one).
In terms of aesthetics, Zerg. Got a love a race with the power to vomit purple slime...
In terms of aesthetics, Zerg. Got a love a race with the power to vomit purple slime...