I think I have taken all but maybe 3 of the tours available including "Dine with an Imagineer". They were all excellent tours and would be hard to rate them because each one shows you something different for the most part. In MK KTTK is good as is the steam train tour. Epcot- Both the undiscovered world showcase and even more the undiscovered futureworld is great. The seas aqua tour is a unique experience. Unfortunately they no longer offer an individual tour at MGM any more. The last tour I took "backstage magic" was 7 hours, but was one of the best because of all the interesting things you saw that is not shown on other tours(except the utilidors). In ak, if you want to learn trivia, take Wild by Design if you are interested more in the animals and their care, take Backstage Safari. Of course there are many other interesting tours. One thing I have found out is that a tours success depends a lot on the CM guide. For example, I have actually taken the KTTK three times over a period of years. One tour was great, the CM knew and conveyed a ton of interesting trivia. On the next tour, we didnt get half of the info as we did on the first. I know that all the tours are scripted to a degree but some guides just make it more interesting than others through knowledge or their personality. 99 percent of the time, they do a great job.
If you would like any details on some specific tours, dont be afraid to ask!
Lancer