Based on the added skills, items given, etc. what is the best type of class (Mage, Rogue or Warrior) for either the Vampires or Dawnguard? Also, what skills are really helpful to have already high before you join either?

I am trying to build some PC's to play both sides while waiting for the PC version.

Thanks.

I was going to come in here and suggest one with a damn good cooling system, but I got the wrong gist from the thread title

I think a spellsword is the best way to go, with a smattering of archery. You can use the crossbow, you have a large magicka pool for the VL form (even though you get a very large magicka buff anyway) and you can still knock heads together the old fashioned way!