HDMI Output Quality

I appreciate this is not specifically Linux/Ubuntu related but I am sure I will get some useful feedback.

I have a new laptop, dual boot of Vista and Ubuntu, it has an hdmi output so my question is;

If I have some HD video content on my computer and I output it onto my 22" LCD TV screen am I likely to notice a difference if I use the RGB monitor cable to connect or an hdmi cable.

I appreciate the convenience of sound and video on the same hdmi cable but am wondering if the difference in output quality (If any) is worth the purchase of an extra cable.

Geoff Lane