I've been debating if I should add a preloader to my page that hides all of the page's content until it's loaded. Once it's loaded, it fades out a full-screen overlay to reveal the site. Is that delay in seeing content beneficial or harmful? Does it work on certain sites better (ie a smaller portfolio site vs a big news site)?
Loadmasks (the category to which a preloader belongs) have two main functions:
So if any of these two is your case, preloader would be beneficial.
Against preloaders is the fact that they delay users' scanning and interpretation of the site content - if what's there before the site load could in anyway be meaningful for the user, you may wish to rule against a preloader.