Both are 5m selling #1 lead singles which also sold ~10m WW (this might be outdated idk but either way they're still pretty close). Obviously you can't compare the streaming numbers since Roar DESTROYS WFL on YT but as you know YouTube is continuously growing and is exponentially bigger than it was in 2011.
Anyway, what was the bigger hit? What's your fave? What's more iconic? Decide, ATRL.
We Found Love spent 10 weeks at #1 on the Hot 100 and spent 12 weeks at #1 on Radio Songs. Roar was only powerful in regard to streaming and digital sales.