I don't have direct experience with either item; the website states on the Randonneé's:
The cut of these Rapha City Shorts is more generous than in previous seasons. For the perfect fit we recommend downsizing by one size.
I'd imagine the reason being increased comfort for longer riding, whereas the Cotton Shorts are more casual on/off bike city wear and fit a little closer.
I don't have direct experience with either item; the website states on the Randonneé's:
The cut of these Rapha City Shorts is more generous than in previous seasons. For the perfect fit we recommend downsizing by one size.
I'd imagine the reason being increased comfort for longer riding, whereas the Cotton Shorts are more casual on/off bike city wear and fit a little closer.