26" gives me greater comfort on tour due to the shock absorbing effect of the higher volume/lower pressure tire. Riding cracks in pavement and broken shoulders are not so hard on hands, wrists, shoulders and butt with 26" when you are experiencing that all day.

I think tire technology has come a long way in the last dozen years, in part thanks to Schwalbe. On two of the bikes I use for loaded touring I run 26 x 2.35 (Schwalbe Fat Frank) tires that are sufficiently flat resistant and grippy in all conditions. Also, my experience is that a tire that wide handles the weight of the load better than the 700 x 35 (Panaracer Pasela) I use on my LHT. When those 700 x 35s are worn I expect to replace them with Schwalbe Marathon Dureme.

And a final reason for me - my 26" touring bikes have flat bars (Surly Open Bar) which I have found more comfortable for a long day than the Nitto Noodles (drop bar) I use on my 700-tired LHT. I am not as aerodynamic on my 26" bikes and that could slow me down but I sit in a position that is better when I am riding all day. I realize many people say they find drop bars better and I like drop bars fine for shorter rides but not for all day.