I have Panaracer RiBMo's (26" x 1.5 up to 80psi) on my LHT. I commute year round and haven't had a problem, but have never toured on them. The Schwalbe Marathon Plus are also highly recommended.

When test riding bikes the 26" wheels felt slower than the 700cc, but they were also different tires on different bikes. Maybe try a search and look for responses in the touring forum.