key binding question

[Hadron]

Is it to add a new key binding to be local to a specific mode by adding
a hook e.g


(add-hook 'html-mode-hook
          (lambda ()
            (local-set-key [f10] 'myfunc)))


or to use define-key on the specific mode-map?e.g

(define-key html-mode-map [f11] 'myfunc)

(assume the html-mode-map variable is instantiated/inscope.

Or to ask another way, why would you choose one over the other and what
might the pitfalls be?