Chromium is actually a translucent coating applied over the nickle coating underneath and that is what gives it the shine it has. It is also only a mil or two thick so much care should be used when polishing with anything that is an abrasive because burn through is very easy to do and cannot be repaired without rechroming the piece.
I never use anything other than Pledge or liquid turtle wax in the green bottle on chrome for this reason. You can't polish out an imperfection in chrome without damaging it in some way.
IMO anything like a chrome polish has an abrasive in it and unless you are trying to remove a stain on the chrome, you can only detract from the glossy finish using an abrasive.
The appearance of chrome that has seen the use of a chrome polish (abrasive) when compared to a piece that hasn't been exposed to the polishing will be evident in the sunlight.