Get one with good sights.
Whatever kind you get, I encourage you to get one with a good set of high-visibility adjustable sights. User-friendly sights won't instantly make the beginner a better shot, but it certainly shortens the learning curve.
GP-100s come with adjustable sights, as do the Security Six series. In addition to being easier to learn the fundamentals with adjustable sights, they'll allow you to use ammunition which shoots to different points of impact. A few clicks on the sight screws with a screwdriver, and you're back in business. With fixed sights, one must remember how much to elevate or depress the sight picture to adjust to ammo types with different points of impact.
Of the firearms mentioned, I'm inclined to go with a GP-100, or Security Six. Every Ruger revolver I've ever owned or fired has been rugged to the point of ridiculous, accurate to a fault, and remained so for all the years I used/owned them. Taurus has a lifetime repair policy. Ruger revolvers don't seem to need one. Taurus revolvers are largely patterned from S&W revolvers, which have very tunable inner workings (which means it's easier to obtain a beginner-friendly trigger). Ruger revolvers tend to be built from fewer, more robust internals, which makes them very durable, if not quite so easily tunable.
I would also suggest paying extra $$, and getting the revolver in .357. You may shoot .38 Special loads in it 99% of the time and be fine with it, but you should have the option of more power if you decide one day that you need it.