Who wins?
Stacking a +4 on a +2 vs Draw until you can play
Draw until you can play wins 68% to 32%. 54 more put them in the same row. From Board Game Rule Debates Tier List. Pick a side.
retired_pickle on Stacking a +4 on a +2: if you allow stacking, color doesn't matter
throwaway80548 on Draw until you can play: makes rounds faster when someone is sitting on 2 cards
Board Game Rule Debates Tier List: the full ranking