I'd say you can't really compare them. Like Mario said: Wax is more for stuff like keying and masking. You wouldn't do that with Virtualdub.
As for me, I'm using VD and I'm really content with it. I don't only render the pictures to an animated sequence (as I am working with a Canon EOS which is not connected to a PC whilst shooting), but do several effects. There are a lot of filters out in the internet that can be downloaded for free, for all kinds of options. Not only stuff like a deshaker, deflicker etc. filter; but I do also zooms, pans, color correction and a shaky-cam-effect with it. Moreover, the program can handle very high picture quality.
I would really recommend you trying out these programmes, so you can judge by yourself which one you think you can need and which not.
- JD