Touring Plans is a business. They have books, a website, app, etc. They have several members on their team who visit the parks, gather data and offer customized planning options.
WDW Prep School was started by a lady who was a member of TourGuideMike and she started it when TGM shut down. She uses that methodology. (at least the last time I checked)
Both are good sites and both offer good information. You will most likely find differences as well due to different methods of coming up with information.