Subscribed to both online and bought the UG (though not recently; I probably have four or five previous copies lying around the house).
My advice: if you're going with just the online content, go with Mike. Mike has a huge amount of material available to subscribers -- it'll take you weeks to digest it all.
The Unofficial Guide site (
www.touringplans.com) makes a good companion to their guidebook, but it doesn't really make the cut if you use it as a standalone.
As others have said in different ways, TG Mike lays down some very basic "rules" for touring the parks, then builds on them and explains how you should use them to your best advantage throughout your trip. He's very into having his subscribers understand how the parks and crowds work, how to best use fastpasses and how to avoid falling into the time traps that foil most WDW visitors.
Len Testa and the Unofficial Guide folks seem to be more fixated on conquering WDW with statistics. I think that the jury is still out on how well you can make park touring into this kind of exact science. To their credit, these guys spend a tremendous amount of time and energy gathering info about wait times, hotel occupancies, transportation times between resorts and parks and all sorts of other Disney experiences. But I'm not sure that the whole -- meaning the touring plans and best-days advice -- ends up as compelling as the amount of work that goes into its parts.
In the end, you'll be better-prepared than 95% of the other tourists who visit Orlando (and who generally show up at the gates and say, "What'll I do now?") if you read and follow the advice from either source.
Hope this helps...Have a great trip!
Bruce