I've got a 640 Pro and 642. My four holsters are:
OWB - Desantis thumb break scabbard - my favorite. I wear it in the high ride position. In fact, I had the "low" ride loop cut off by a local shoe repair shop.
IWB - Galco Stow N Go
pocket - Desantis Nemesis (preferred) and a Mica
I recently tried a Desantis Flex Tuk, bought from Amazon. Didn't like it as well as the Stow N Go, so I returned it.
I rarely pocket carry my J frame. It fits, but the Carhart jeans I wear don't seem conducive to it.
I like the Desantis thumb break scabbard so well I'd never use anything else, except it takes a sweatshirt or baggy untucked shirt not to print, and I don't like people to know I'm carrying. Plus I don't care for the untucked tee shirt / polo shirt look in warm weather. The Galco still requires an untucked shirt, but rides nice and low and doesn't print.
Good luck with your choice.