What sort of a group sighting in with a rifle do you find acceptable at 100 (or 75) yards?
Make sure you are capable consistently of that before you feel you are ready to go it with a handgun...
An advantage with the .357 is being able to shoot more frequently with inexpensive loads to develop your skills. Alot of guys who try to learn on full magnum anything never are able to hit the inside of a barn because from the first shot they flinch. It takes time to develop handgunnng skills- alot of it.