интересоваться, being a verb implies active action on the part of the subject and being imperfective implies some history of being actively interested in something.
интересно is a passive construction and so may mean just a momentary curiosity (though it doesn't exclude active interest).
If the words mean an object of curiosity,
вам интересен .. ? means
is it interesting to you and
вы интересуетесь means something like
do you have a hobby/professional interest.
If the meaning is that of 'benefit', you would ask
вам интересен if you're offering a deal to an unsuspecting customer (i.e. hoping to incite an interest) and
вы интересуетесь is what e.g. a sales assistant in a shop would ask, seeing that the customer is already in active search for something.
вам интересен is asking about the person's reaction to the (grammatical) subject and
вы интересуетесь is asking about the person's objects of interest.