As far as I know the Radeon is the only one (among the low end capture cards) that does hardware accelerated encoding while doing captures, as an ex Deluxe owner to my knowledge Asus still uses a low end capture chip that does the encoding at the software level.
My opinion is that the capture quality is better on the Radeon for the above mention reasons. For the life of me I can't find the website that did the review on the capture aspects of the radeon that would show the difference. I'm not saying that the Dlx is junk but between the two, the radeon is better. IMO.