The 357 guns are in demand by cowboy action shooters so they can shoot free, range pickup brass in 38 Special, to include lowest powder expense and cheapest bullets. They also have a shorter throw when cocking the rifle, tuned to run well with extended 38 Special (crimped forward of the crimp groove). I would go right for the 45 Colt if not into cowboy action (maybe you should try it). The 45 Colt would make a great introduction to reloading. The big case is easy to handle and powder charges of mid to lofty fill volume are easy enough to see before placing a bullet. Basic reloading equipment would be very affordable, with the Lee Cast Turret getting my vote for modest volume use.