You'll probably want to use the full screen mode, I assume? At full screen, the picture doesn't acheive the sharpness that a TV gives, but the picture is rendered at a better resolution than that of a television (640x480). When viewing the image in a smaller windowed screen, especially at a resolution such as 1024x768 on your 17", the quality looks pretty descent. In my opinion, the windowed screen can superseed a television image in quality if you have a good receiver (read: not rabbit ears).
I have no experience with the USB tuners, but I'm plenty happy with the PCI cards. I'd expect the USB to equal the PCI in quality. As for which version to get, I would say it depends on what other peripherals you have attached to your computer. If you have, or are planning to get other USB devices and you have a free PCI slot, get the PCI version so you don't take up a valuable USB port. On the other hand, if you're nearly maxed out of PCI slots, but you have little or no USB devices, get the USB version.
-CamaroGuy