Is it better to buy an internal or external device for capturing video, and does it make a difference in the quality of the video.

Also, I've had some issues with capturing and editing video with the video quality. Is this usually because of the device, DVD or DVD player, capturing software program, or video editing software program?

I had a cheaper device from Tiger Direct and the videos aren't coming out very good even with an S-Video cord. I was wondering if another capture device would change the quality that much?