Unless the point of my tour was to be a photography expedition... I'd go as small as possible. I usually carry a small digital with manual controls like the Nikon S90/100/110 and it suits my needs on a tour. I wouldn't hesitate to take an SLR/DSLR along if I planned on spending as much time behind the view-finder as I did on the saddle. It really depends what you want out of the tour.