When I compare PQ of Component vs HDMI I would say there IS a difference, but not big.
And since it is a digital connection kickoff handshaking leads to a lot of switching noise, snow pics and garbled frames before hdmi finally settles after a few secs.
Also, my Marantz DV-9600 player sometimes refuses to put out a hdmi pic for no apparent reason, so when that happens I have to switch over to component!
It's not the Marantz (same thing happened on a Pioneer DV-989), nor the scaler, it's THE SYSTEM...
So don't worry too much if you don't have it...