EaW because it has better balancing, and fewer game stopping bugs.
I fixed that for you, which was clearly wrong. Unless sarcasm was involved, at which point you are absolutely correct.
Nevertheless, FoC is the better game, just for the fact that it expands upon this game (hence the term 'expansion pack') --- Call me Xan. If you don't, my beatin' stick will be your friend. Supreme Voxman of the Xavion Corporation
The ZC is overpowered, but the Rebels and Empire are better balanced vs. each other in FoC. AT-ST's had their damage vs. infantry increased so they don't have to use a full barrage to handle large groups and are not destroyed as easily by Plex Soldiers, AT-AT's no longer slaughter vehicles as easily as they did in the original, the Empire has better anti-air capabilities(Speeders were the single most annoying unit from the original game because Empire units wouldn't auto-fire on them, in the expansion it's replaced by corruption), both factions got MDU's, which are great for low build pad maps like Korriban(can anyone say rocket turret on the ledge overlooking the enemy landing zone), etc.
The base layout screen is probably the best addition though, which gives you a tactical advantage/disadvantage(depending on how you setup your buildings) when defending the planet.