If I live in City X and there is a really tight race between two candidates, and one of them wins by a hair, then you’re saying that all of the people in city X now have the person representing them being weaker in the legislature.
I think OP is saying that City X would have Reps 1, 2, and 3 (etc), and that (in your scenario), 1 would have a slightly stronger voting power than 2, while 3 had less power again.
This would mean that almost all voters in the city had some representation that they agree with, but with power apportioned proportionally.
Compared with City Y (same population), where candidate N won 99% of the vote, N would wield more power than 1, 2 or 3 individually, but the same amount of power as 1, 2 and 3 combined. So the city’s representations would be equal overall.