I don't know if any of them is more accurate than the others. One thing I do find helpful is the actual Disney website, specifically, the blackout dates. Those are generally the busiest, AND the weekend after a blackout date because the APs come back in after a hiatus. Otherwise, you can apply a couple general rules of thumb and get a good idea - weekends busier than weekdays, holiday weekends busier than that, etc. There are some special events to take into consideration, such as large conventions, but generally, I don't find any of the crowd calculators to be full of knowledge.