All four of the barrel-makers mentioned (McLennan, Gaillard, Smith and McPhee) make world-class, benchrest-grade, hand-lapped barrels using the finest steels. Period. They are comparable to Krieger, Lilja, Shilen, etc. -- the finest U.S. custom barrel-makers.
Just a personal opinion, but I'd rather support local craftsmen whenever possible in order to keep our sport (and the necessary infrastructure) alive in this country. The prices these Canadian makers charge for their barrels are actually less than you'd pay for a comparable U.S. barrel after exchange and import hoopla.