In principle, the 0W-30 may be more prone to shearing out of grade (so that is is no longer a 30 weight). But the SuperSyn formulations have generally looked pretty resistant to shearing down. This is probably only a concern for very long drain intervals.
If you lived somewhere extremely cold (like Grand Rapids) the 0W-30 would probably be better in the winter.
Most places and most uses, it probably doesn't make much difference either way. If you can get the 5W-30 in 5 quart jugs at Wal-Mart, it will be cheaper than 0W-30, so I would go that route.
