Tango or Oovoo video chat for iPhone?

Which app is better? Regarding lag, quality etc. If it helps I'm wondering about specifically between two iPhone 4s's.

For computer i say Skype…

For Iphone i say Tango because oovoo isn't that good with calls

I've used Tango and if you want free calls just take of the video and you won't get lag

Oovoo 4 me

Tango or FaceTime?