The general consensus is it only makes a real difference if you PvP. The undead racial ability, will of the forsaken, can be game-changing in PvP, where 1/3 of your opponents will be trying to fear you. Other than that, no biggie, play what you enjoy. Each racial ability is a minor advantage that is not immensely greater than the others. I myself play a troll mage because there are too many undead and belf ones, and I do fine in PvP even without the game-changing ability I referenced above. Plus, I dig having a rasta-man.