Offense. Ambiguous vortex setups are getting abused even at high levels and tournaments. Blocking most of these setups isn't imposible, but it's ridiculously hard. Properly blocking stuff that's so ambiguous and difficult does not reward the defensive player in these situations as much as I think it should.
Off topic, but it's hilarious how the same people who abuse the fuck out of these setups (especialy the ones that are totally safe), will tell you that footsies and reads is more crucial.