Thanks.
My plasma is wall mounted and so it is not an easy matter to swap cables around to see any differences.
This thread
Component VS RGB Scart, gold co-ax etc
seems to suggest that with my set up (ie a cheapish DVD player and a goodish plasma) component is only going to be mariginally better than scart.
I will probably go with scart.
Next question is whether a 5m length would be appreciably worse than a 3m length? (Richer Sounds, where I need to take the component leads back to, only do 1.5 or 5m lengths - I will have to order elsewhere to get a 3m length)