The privacy issue with Qihu has been refuted by them, and so far it's hard to say if they're true or not, but it's not like there's a smoking gun, from what I could gather. I'm no specialist nor have I looked at the issue in detail.
But, I vote for Baidu. Up until today, my vote would have been neutral, both AVs with their qualities. But Qihu 360 IS has a terrible design flaw: it's Proactive Defense doesn't work without the internet. That's right. No connection, and no detection, means no defense at all. So if you bring a USB from work or college or a cyber cafe etc., and plug it into an unconnected PC, Qihu 360 IS won't help you. Baidu AV, on the other hand, shows no difference in its Proactive Defense between being online and offline.
A member of Wilders had noticed this and contacted their support. Apparently this is not a bug, they said it is by design. Design flaw, in my opinion. So, between the two, I'm with Baidu at the moment, they who started out with serious update problems, but now seem to be fixing them.