When it comes to video quality, I'd go for Qik.
Video shooting screen
The frame screen of Qik is bigger than that of Flix. So I won't have to worry about shooting just my forehead (which happens most of the time on Flix), just my nose or just my lips when I shoot a vid of myself talking nonsensely.
Capturing the very moment
Again, Qik has a function of recording videos even if I don't have a current WiFi connection. As long as I start the app, I can record and capture the very moment and just upload it later. Flix doesn't allow this. On Flix, no connection, no captured video.
After Youtube posting
Both Qik & Flix allow me to upload my videos to my SaritaFlix channel on Youtube. But I noticed that Flix vids are clearer than Qik when posted on Youtube. Why? Because Qik compresses the video first into FLV format then uploads it to Youtube. Flixwagon, on the other hand, compresses almost nothing of my videos as it is uploaded in .MOV format.
Both video apps have its plus & minus. But I'd still go for Qik since it allows me to capture the very moment & upload it later. :-)