One's in a much better situation, with similar (probably a little weaker) competition. The other has the greater talent by far.
I think Tate wins this year, maybe next year; Spiller will be the better long-term back.....
I actually would take Spiller in a draft, since he's got way more upside (talent) than Tate, but I voted for Tate because I don't believe the disparity for the next 4-5 years will be all that great, Spiller didn't "deserve" to win unanimously, and if you're looking to "win now" I'd take Tate.
I don't think those are valid reasons for a vote though. Can I change my vote