ATOs or Cobrinha?
I don't know how big Cobrinha's organization is. One thing about ATOS is they have affilliates all over, so if you travel much you might find other schools to train at. I have trained at one ATOS affiliate http://www.convictionmma.com/jiujitsu.htm and was more than satisfied with my experience. I haven't talked to anyone that trained at an ATOS gym and was unhappy with their training.
It would depend on where I was at or traveling to... I have trained with both Galvao and Cobrinha (both come from the same lineage of the old TT days).