What would it take to confirm or refute the Snowball Earth Hypothesis?
In order to confirm the snowball earth hypothesis, we'd need at least:


A paleogeographic model which extends to greater than 650ma and has been shown be be conclusively accurate throughout that entire period. (i.e. one we can trust)
Sedimentation structures/patterns (or other paleoclimate proxy data), consistent with a glaciation event, tied into the same time period, from the north pole to the south pole