The "common knowledge" is that Bonanza parts are more expensive but don't need replacement as often so the long term costs are probably pretty close unless you're extra hard on airplanes or just unlucky. And while Beech's prices for some parts will take your breath away, most of the things that break (vs wear out) are available from aircraft salvage yards at a much more reasonable price. I'd guess that used parts are much more readily available for Bonanzas than Comanches because there were many more of the former built.