We have used both, we prefer touringplans.com/UG. We have young children -- they are now 6 and 4, and we are planning our 4th trip in 4 years with them. We also travel with my 68 year old mother. I have NO IDEA what people are talking about when they say touringplans.com requires a commando style. I assure you my little boys and my elderly mother would not be going for that.
I also have absolutely no idea what TGM people mean when they say TGM provides a "why" but UG doesn't. Obviously these people have never read the UG, because there is a ton of information about ride loading time, tendencies of crowds and crowd movement in the parks, the design of the parks and how it affects crowd flow, etc. in the UG, as well as how the outflow of one ride impacts the intake of another ride, and on and on and on. If you look at touringplans.com and the "crowd blog" you may just notice that Len Testa is basically a PhD on the subject and bases his predictions on no fewer than 30 odd variables that may impact crowds and crowd movements. If anyone needs a better or more thorough explanation of why touringplans recommends the order of attractions they do, they need to have their head examined.
Finally, with regard to the OP -- the touring plans are very (some might say "remarkably") similar IMHO (I subscribed to TGM in 2004 and 2005), although UG and TGM crowd level predictions/best parks best days may differ. Why do they differ? Because Mike is in the parks and making his judgments in a qualitative way, not in terms of qualitative research. He is using knowledge he has gained by experience in the parks. The UG researchers have this too, but add to it significant quantitative research, some results of which have been published in peer reviewed journals in statistics, etc.. They also study a much wider data set -- weather, school closings in Florida, car travel numbers from
AAA -- than TGM.
I should also point out that touringplans.com makes it clear that "best days of week" for the parks has a relatively minor impact, compared to the major touring impact of getting there by opening, for example, so you shouldn't stress out over it.
I personally think the UG is a better value for your money and gives better advice, but you can purchase TGM and get a refund if you don't like it. Have a great trip!