Of course, both sides have their ups and downs. "Sharding" your world, a term that derives right from the lore of Ultima Online, lets you deal with a smaller community, make close friends, and have a more "shared" massive experience. However, should you not play on the same world as your friend, you're never going to get to see them!
One server, on the other hand, lets you meet everyone who plays the same game as you. Simply by switching instances you can have an easier time finding a mob to spawn or a clear area to camp. However, some say that this detracts from the community of a game, as instances aren't as personalized. Or, in the case of EVE Online, you're one pilot stranded in the lone universe.
So what's your opinion on this war, dear readers? Comment and let us know!