+1 Furry.
And yea, the shorter the better, but the exact length means nothing. Its just more pre-made ethernet comes in 1,2,3,5,7,10,15,etc lengths. I personally like to color code mine too, make my WAN blue and my LAN green. But thats because I learned on Linksys Equipment who make their WAN(Internet ports) blue, and LAN ports green. Dlink happens to do the exact opposite, but the color of the wire doesn't mean anything, its just so you can know by sight where a wire comes from ya know? Its the same thing with the length, its just personal preference.
Simple answer? If money isn't a issue, get CAT6. Otherwise get CAT5e..just don't get CAT5.