Nar the Ultra bags do filter better than the paper bags.With paper bags the housing gets coated with dust I've seen it with my own eyes. I had a demo of an X4 about 6 years ago and remember when opening the bag housing it was covered in dust. Speaking to a member with Ultra bags they told me this doesn't happen now which is what I find with the Felix ultra bags which seem to be improved further with my new batch. Miele bags are very good for this too.
But to get the definitive answer I will email Sebo and ask them if the Ultra bags filter better than the paper bags as I may be wrong. 
There will be a discrepancy between different manufacturers test ratings but Sebo tested the Evolution and G series and found the G series performed a little better on carpet. [this post was last edited: 3/1/2015-01:56]
