Accout info for most of these games is stored serverside, so you'll have to re-install the app itself, but you'll be able to log in normally once that's done.

Now, if their smart they'll allow the game to store map and general graphics info clientside as you pass through zones for the first time, hence speeding up loading times each visit thereafter... If you re-installed the game under those circumstances you would find it a bit laggy the first time going to all your favorite spots for the first time on your new system.