There are a few differences. In my opinion, the most important feature that is lacking in the Qanvee is that the sponges are not magnetically detachable. This is important for me as I remove and squeeze clean the sponges for the discus tanks very often.
Qanvee does not come with media, which is not an issue for me as I do not use the BioSpon filter media that comes with it anyway.
I am not sure about the Qanvee, but I find the materials, build quality and the sponges of the BioSpon to be of very high quality compared to typical sponge filters.
So... without the magnetically detachable feature, the Qanvee essentially is just like any other sponge filters on the market, which are generally not known to be great mechanical filters. They are more superior as a biological filter.
Personally, I would either buy a BioSpon (pay a premium) for its features, convenience and superior quality or buy a normal $5 sponge filter which provides good biological filtration.
Just my two cents. :)