You're going to love it! Get some snap caps(not actually required, but prevent loaded ammo from possibly being in chamber) and dry fire it until your trigger finger won't pull the trigger! Do this every night or every other night, as much as you can stand. Occasionally point it at something and squeeze carefully so you don't ruin your trigger pull. The action on TV works great. After you do thousands of trigger pulls, the trigger will be smoother and your finger stronger. It's win-win and you'll be shooting that puppy like a champ!
I didn't think the GP100 trigger was that great, until I handled a used one. They really get better with age and use!
If you don't reload, .357/38spl is crazy easy to reload for and you can get started cheaply. With a budget minded set-up, it can pay for it's self very quickly.
GP-100 stainless steel. Have looked at and handled the 686's, Md 13, Md 60, Md 64 and Md 28. Still for guys with big hands the GP-100 is great.
My fav is the older ones with gonvales( or however it's spelled) inserted grips and stainless steel. The SP-101 is the same quality on a smaller frame.
A 3 inch barrel is an interesting choice for a range gun. The 3in GP100 has fixed sights that wouldn't be ideal for a range gun. Between the two you listed I personally would choose the Ruger. I'd choose the 4.2 inch barrel though, not a huge fan of the 6inch.