I once measured my rep and gen 16710. Rep was 2 grams heavier. The older reps were even heavier because of the solid middle links on the bracelets. And there's no weight difference between the clasps. How could there be... I mean, they're both sheet metal which feels cheap and light anyway.
Generally... all that usual talk about weight differences is total and utter crap as well, spread by people who don't know what they're talking about. I don't know where this myth comes from and why it's still alive... maybe from the 80's when quartz-powered reps really were lightweight. Same thing about the "dramatic" steel color difference... you gotta be a real Trekkie bastard to see any. "Rolex steel"... they're so special... it takes a year to make one, etc.
It's true that the bracelet "feels" different on the gen. Mainly because of the smoothed, rounded edges. But that's for another discussion.