As the bull barrel versions are a bit heavy, you might want to consider getting one of the three with a standard barrel for beginners.
I agree. There should be an assortment. When I taught my children, we used a wheel gun, a Colt Woodsman semi, and a bull-barrel. Then we moved up to my Ruger Blackhawk .357 shooting .38, then loaded up on hot .357 rounds.
Final step were with SIGs in 9mm.