I'm another one who thinks that you need to pick your tires based on your personal situation and needs. For me, flat resistance has always been a primary concern. I'll gladly trade off a little smoothness and put up with a little more buzz and tire weight to get it.

For one, 99 plus percent of my riding has been solo, so if I get a flat, I am on my own. Oh, yes, I know how to fix flats out on the road and have done my share of them, but as I'm sure we all know, you always seem to get flats at the worst times. Changing a tube in the dark with just the aid of your bike light just isn't fun.

For another, I have lived in some serious thorn country (prairie states) where even thorn tubes, inner tube goop and thorn liners were no guarantee of not getting a flat. Soft, low tpi tires wouldn't last a week. Just because this isn't an issue where you live, doesn't mean you won't encounter these locations when you take off on your cross country ride.

For a coast to coast ride, a standard road bike with 23mm or 25mm or even 28mm would not be my first choice, anyway, but I'm lucky enough to own a number of different bikes and not everyone is. That, and plenty of folks have done such a trip with 23mm tires with no issues. Just a matter of taking a little extra care when riding.