Well, presuming you mean VGA when you say PC socket, then that is analogue and HDMI is digital.
But no, there's no great difference in video quality, presuming your TV can cope with the full resolution from both inputs (not always the case).
If you have an HDMI output on your PC then you can send the audio down that as well, so you only need the one lead, whereas VGA always requires a separate audio lead.
You might see differences if you are using a long cable though (over 5m).
Digital is more likely to faithfully reproduce the picture in that case.