I have Ruger LCR in 357 but I shoot 38 special +P. It works well. I have sold LCR since it had more recoil with the same loads.
Calibers? 9 mm is good, 40 sw even better, 357 mag and we can go on and on and on.
Choose what you like and fits you. In my opinion 38 special and 9 mm are great self defense calibers for small weapons.
Have fun, Vodek