You should go with a warrior, because you have much better survivability, mobility, utility, and overall greater damage. Plus you don't need that much skill to play a warrior, the DPS rotation is easy and you do not need to worry about rage starving unless you are playing in defensive stance. While playing on unholy death knight you need to manage your pet, manage runes (witch don't work that well), stack necrotic strikes and you can't just spam your abilities like you can do on your warrior.