Not if you're buying the X for the out of contract price. In that case I think the Streak might end up being cheaper.
But anyways, I think the X might actually be a little bit of a more powerful device. I don't think the Streak has a 1GHz processor. Also, though I like the Streak's UI, I think it's a little more clutter and less customizable than XBlur has been shown to be.
All in all, Jubba is right, two totally different devices. I think if the Streak had a 8" or 9" screen, I would buy it as a dedicated tablet PC, but it's more of a giant cell phone so screw it.
EDIT: I image talking into the Streak would look a little like this:
YouTube - Trigger Happy TV - Phone + Toilet