I am fond of the Model 19. I prefer adjustable sights and the shrouded ejector rod. I think it give the Model 19 a better look than the Model 10
Of course you have the ability of firing the more powerful 357 Magnum ammunition if you want to with the Model 19
In your case, a NEW firearm makes much more sense than a used one. The new gun will come with a lifetime warranty, something that is not included with used guns. Since your 19 year old daughter is the intended owner of this firearm that is kind of important. At 19 she might not have the ability to analyze issues and fix them herself like may of our fellow Forum members. Knowing that it something happens she can send it to Smith & Wesson instead of finding a gunsmith to fix it should give both of you piece of mind
The lock is a non issue for most reasonable people. The lock has been with us for 18 years now. Millions upon millions of Smith & Wessons with locks are out there, if there were any kind of epidemic problem with it we would have late night TV commercials from Lawyers asking us to call in and join the lawsuit.
Yes, there have been a few lock failures, but we hear about many more ammunition failures, hands that break, trigger or hammer studs that break, etc. It is a mechanical thing and mechanical things break. If you want the least chance of a firearm failure, we would probably have to go to a single shot to avoid all of the common failures of innovations over the last century.
However, the lock issue gives lots of folks reasons to argue on the Internet. I see no need to argue, the lock is not an issue to me so I buy guns that have been made over the past 18 years. If someone is afraid of the lock or does not want one . . . all they have to do is not buy one.
The newest (in terms of manufacture) Smith & Wesson that I picked up (last summer) was manufactured in January of 2019 and I am very happy with it
The Model 19 is a gun that will last her a lifetime if properly cared for. You will probably see the day that she passes it on to her child next