Depends on your taste and the situation. If this were a hard user, not rare, and there were a series broken ribs, replacement would be the best option. If it's a pleasure canoe for use on lakes, rare, and only one rib is cracked as it appears here, a backside repair might be best. Your canoe is probably somewhere between these to ends of a spectrum. Still, after seeing the photos if this were me, I'd do a backside repair. It's quick, easy, and done well it's strong. Plus everything is there - this isn't a displaced fracture with missing wood. Whenever I've done such a repair a crack in the bilge like this, I back it up on the inside with a custom-fitted block of wood (covered with plastic so it's non-stick) to restore and maintain the proper curvature of the rib.
Michael