I agree that it depends on what you're ordering. Just like Disney, the dining plan is meant to be a convenience rather than an outright savings. So while it COULD be a savings, you may lose money or break even.
The QS plan made sense for us one day last trip. At Universal, you can purchase the dining plan as you go. We purchased it while dining at Three Broomsticks because 2 adult QS plans cost the same as what we were ordering, and it gave us two snack credits to use before our trip ended. So that was a good value. If we hadn't been ordering the expensive entrees or butterbeer, it might not have made sense for us.