I can't imagine a better choice than a Model 10. Smith and Wesson is known for making revolvers, and the Model 10 is the one they made the most of. I have a couple of them. Even people that aren't into guns probably think of a revolver when they think of Smith and Wesson...and they probably envision a Model 10 without even knowing it.
I got my girlfriend into shooting, she doesn't like semi's because the slides are hard for her to rack, and the manual of arms is more than she wants to learn right now. I wouldn't want her depending on a semi unless she was totally confident with clearing malfunctions anyway. She LOVES the Model 10...and she shoots it very well. She also shoots and carries a 642, but it's the Model 10 that she loves to shoot. Not too much recoil, not too heavy, and an easy manual of arms. She's not "intimidated" by it like she is with semis or heavy recoil guns. We bought a Pachmayr rubber grip for it...but soon returned to the wooden grips with a grip adapter....it just feels right. I've also taught several people to shoot with the Model 10, including a couple of kids whose hands were small...they loved it too. It's just a great shooting gun.
I love revolvers, even though I probably have more semis than I do revolvers, I just love their simplicity and ease of use. Great for teaching new shooters.
Heavy barrel, pencil barrel, I don't think it matters really...you'll want both eventually anyway. Both of mine are heavy barrel...but I would like to find a pencil barrel in decent shape for a good price.
Many, many years ago, back in the early 90's, I went to police training. For pistol qualifications they would supply the ammo if you shot .38 or 9mm, and if not they would supply a gun... a beat up, ugly, Smith and Wesson Model 10 .38 Special. I only had a .45 and a .32 at the time, so I had to decide to supply my own ammo or shoot one of their old ugly guns. I didn't have much money so I chose to shoot their beat up ugly revolver. I really liked semis at the time...so this was a disappointment to me. One of the guys in my class had gone out and bought a new Glock, .40 cal I think. He had shooting gloves and everything. I think I dropped a round or two on the day qual, I don't remember. On the night qual I shot a perfect score...and with that beat up old gun they let me use. I didn't see the kid with the Glock. When I asked where he was someone told me he was sitting in his car crying... I guess he really took it tough.
Old Model 10's and other old revolvers have been getting the job done for a while.
Good luck, and let us know what you decide on!
Fox