MPEG4 Capture & TV Tuner (Plextor ConvertX PVR PX-TV402U & Yuan EZDVX 480)

I read lots of reviews about the ATI 550 chip, and so far this is my front-runner in deciding for a TV Tuner/Video Capture Card.

But I also came across the following they are both hardware mpeg4 encoding:
1) ConvertX PVR PX-TV402U
2) Yuan EZDVX 480

1) I am wondering has anyone seen these or compared them to the 550 (Picture Quality, etc)

2) I am assuming because mpeg4 is compressed format, the picture quality might not be as good as mpeg2? Is this true?

On a side note... with regards to TV Tuner/Video Capture Cards... is there any advantages/disadvantages when choosing a USB vs. PCI?