Oh yes there is. Big big difference.
AIWs use ATi's own Rage Theater chip that has excellent image quality and some neat de-interlacing and filtering hardware, while the TV Wonder series use the Joe Average of video-in chips, the Conexant (formerly Brooktree) BT878 or 848.
Plus the AIWs obviously don't generate any PCI or AGP bus traffic for moving the TV image onto the graphics chip.
regards, Peter