My thinking is that shorter cables are better than long cables. If you do end up getting reflections, you want them to be as quick as possible. The longer the cable, the further horizontally the reflected pixels will be from the original pixels, and hence the worse the image. This is why manufacturers can get away with having non-coax , nonshielded video wires inside the chassis of their components: they may be the wrong impedance but because they are so close to the source, the reflections are too short to cause problems.
Of course having said that, the difference between 1 foot and 6 feet is probably almost completely unnoticeable in terms of reflection timing at HDTV or lower frequencies.
So go with the shorter cable if it's convenient.
You can email me at: tmorrow at us dot oracle dot com