I typically like both, oovoo a bit more than skype because you can have group video chats without having to pay for much.
I like skype because it's easier to text chat and video/voice chat at the same time.
skype because oovoo is loaded with ads and can be glitchy as hell ive tried it just for the group video call did not work to well lagged like a bitch D<.
I have never heard of oovoo before and I just checked it out, it seems quite okay. I have skype and sometime it's a bother, really. =.=; I only skype my siblings though.