The crowd calendars are really no better than an experienced guest taking a guess. In fact I'd say that guest has better odds because they're able to consider real-time details that are better indicators than historical data (like changed EMHs, night show schedules, new rides, etc). I'll view them only to see if I over-looked something on our dates. TP and KtP has other services that are more useful. Mid-week's usually the least crowded and weekends more crowded anyway, so it's always a personal choice to decide which parks you'd best enjoy on those golden mid-week days. The right answer depends on what your priorities are, like seeing MK fireworks during party season, doing FoP without a FP, or if you have a park hopper.
For which weeks are best, look at WDW's pricing. Expensive day, expect it to be crowded. Cheaper days, less crowded. And the more crowded WDW expects it to be, the more hours the parks will be open which helps spread the people out, sometimes even better than off-season short park hour days.