They definitely do both need to be carefully inspected.
I've always thought that S&W advert was very clever. Even though based on their respective websites, the S&W is lighter by only 0.3oz.
However, this is what my scale gets:
6 shot GP with aftermarket sights fingerless Hogue monogrip
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7 shot 686+ with aftermarket Hogue Nylon grip
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Both are unloaded, btw. I'm sure we can work out which would be heavier when fully stoked.
But for a lighter weight and sleeker option, there's this GP100, which I bought used maybe 8-10 years ago.
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It didn't require any springs or shims, or even an action job. And it has the shortest DA trigger of any GP100 I've owned. Though the SA trigger has a step of creep to it. Not too bad of a thing, if you know it's there.