They're constructed very well and are rather lighter in weight and looser in weave, so they breathe pretty well. Denim is slubby, rough, and hairy; a new specimen if you haven't experienced anything aside from APC's.
They do however, have a considerable amount of natural cotton stitching, so it won't last as long as the more common poly cotton stitching.
Go true to size or down one. Find yourself between sizes, get the smaller size, these will stretch.