Excellent question! Park Savers had spent the last 10+ years keeping track of who sells the cheapest Disneyland tickets online. While there are several wholesalers as you mentioned we love and highly recommend Get Away Today. The main reason we like them the most above anyone else is because of their Best Price Guarantee.
This essentially means you’ll get the best price on tickets no matter what. If you did find a better price they would match it for you. Nobody else offers this service to their customers and that’s why we recommend them.