While what kind of information each command displays is probably best left to each individual mud administrator as an exercise, this does bring up an interesting point.
If the players are allowed to switch interface styles, some care should be taken to ensure that the same data is presented in each set of interface code. Otherwise, it's a potential open exploit from the game designer's point of view.
A different interface style (IF player selectable) should only change the appearance of the data, or possibly the command parameters of the input.
OTOH, if players don't get to pick their interface (or only get a limited subset of them), then it might be quite appropriate to have commands show different data detail in each one. For example, if do_look() were moved into an interface, all the mortal ones would show the usual set of descriptions, possibly exits, etc.... but an immortal interface could also show extra descriptions, room vnums, door destinations, and other useful things for the builders.... without having to turn do_look into a mess of case statements.