SPOILER ALERT! Should I become a Vampire or become partially Soul Trapped?? I don't exactly know what the repercussions are with either choice...

EDIT: It's been 12 years and I STILL GET UPDATES FOR THIS POST!

EDIT: WOOOO THE POST LIVES! LIIIIIIIIIIIVESSSS!!!!

UPDATE: So since I'm still getting comments and many people can't find the answer, here it is:

You should become partially soul trapped, as it makes little difference, and you can always re-enter the Soul Cairn and regain it from a chest; Valacia will even tell you where it is.

Become a vampire and you can go in as one fine, but you'll miss out on other side-quests.