go for looks
the racials are very very tiny margin of difference between them in dps.
make a few DKs for diferent races and wander a bit in the starting zone.
i strongly advise either orc or belf, orc has some good dps racials that u can macro with breath/ERW for extra nuke and great shoulders, belf has the utility racial very welcome in m+
going undead u dont lose much, i for one dont really like the bones sticking out of armor but its ur choice
u can be a blue or green tauren as DK due to special skins only DKs have for each race