Thanks to everyone for your feedback. It seems a new contender has entered the race--schwalbe marathons. I had omitted this candidate for simplicity because my LBS doesn't stock them. I know where I can get them (can't order because to close to departure time), but they raise a few questions:
1. "Marathon" seems to refer to at least five tires that Schwalbe offers: HS, XR, Plus, etc. When people refer to "Marathons," to which are they specifically referring?
2. Are these tires superior to the Conti Ultra Gatorskins to such an extent that I should go out of my way to acquire them? (I can purchase the other tires I mentioned and have them put on when I get my bike tuned up next week. I don't drive, so this one stop bike shopping offers considerable convenience).
One day to decide!!
Thanks again