Because I'm fairly tall and finding extra long ties can be a challenge, I usually use a Pratt knot. It has a nice shape, but leaves a bit more length to the tie. On the couple of extra long ties I do have, I like the Windsor. Honestly though, barring the four-in-hand, I doubt most people can tell the difference at a glance. And like one poster stated, the type/width of tie makes a big difference in the choice.

Good resource: http://www.tie-a-tie.net/