I have a GP100 and think it's a great gun. I've only handled 686s and they sure are a bit prettier. I believe the Smiths are forged and the Rugers are cast (I hardly think this matters, honestly) and the Smiths will have a more traditional side plate while the Rugers will not. Both will probably perform about the same (as in, they will be more accurate than you) but the triggers and grips will differ. That will be your personal preference. Mine has a Hogue on it and it's very comfortable. My understanding is that a GP100 will be preferred if you intend to handload as, in the case of a catastrophic failure, the Ruger will handle it while the Smith may not. The resale value on both will be about what you'll pay for it used.
If you really want the Smith, just save a little more and get it. You won't regret the Ruger and money saved if that's not an issue for you.
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