get returns Collection and is rather supposed to fetch multiple rows.
count is a generic way of checking the result:
$user = User::where(...)->first(); // returns Model or null
if (count($user)) // do what you want with $user
// or use this:
$user = User::where(...)->firstOrFail(); // returns Model or throws ModelNotFoundException
// count will works with a collection of course:
$users = User::where(...)->get(); // returns Collection always (might be empty)
if (count($users)) // do what you want with $users