Object or function in module pattern OO JS?

Recently started writing modularised js and I'm starting to notice the numerous ways one can write them.

I know the core principles of when to use an object literal or function but whats the beneficiaries of writing a module as an object literal or function on a larger scale development? Portability, flexibilty, maintainability?

var filterOverlays = { ..code .. };

var filterOverlays = function() { ..code ..}

Call in another page:

$(document).ready(filterOverlays.init);

filterOverlays();