Hi Terry
There are hundreads of reasons why braid or mono would fit each situation.
Braid having little or no streach and a thinner diamiter than mono for its breaking strain. Will assist with feature finding on a marker float and casting distances. Also brilliant for cutting down the drag from running water. Mono is less obvious in the water, sinks better, and the added stretch helps when playing fish.
French fisheries do not allow braid because in the main the fish are bigger than most are used to playing on 3lb+ rods, with no strech and a strong fish, many a "hook pull"
or as I call them "Face Rip" occurs.
Also braids used for carp angling are in excess of 20lb bs. A teatherd fish is nearly always a dead fish.
My advice is stick with mono on your fishing rods, and use braid on your marker rod. Mono is a lot cheaper and a lot more fish friendly.