I think both sites in some way are common sense, but at the same time - their recommendations don't fit "all".
a few examples about the crowds for our trip in May. First of all - we are going in low period, 2nd week after easter. spring break over, kids still in school, colleges have final exams sessions --- common sense says expect low crowds.
lets go by days and park selections. for those who start their vacations on the weekend - first day will be MK for many of us with kids. sure both recommend different park. can i tell my kids no MK on Monday?
another example - one site says Wed is best for MK b/c crowds will be lower since no parade at 9pm. as much as i love the site - there is now way I would go to MK and not be able to see the parade before the wishes. great idea - just not doable for my family. and i completely agree MK will have smaller crowds that day. no question asked.
common sense - of course MK will be busy in any afternoon from 4pm on. so i will use FT+ for any rides in the evening. i will not stay in line 20 min + with two little kids (2 & 4) - not that my kids are not well behaved or anything - but no kid at that age will quietly stand for 20 min in any line. just not possible.
also for those with kids and stroller - stay in the same park area. don't think about going across the park when people start lining up for a parade or park gets really busy. tried once - i know its impossible. i made dinner reservations for 7pm to avoid the madness in the evening.
if you go to AK - there are 2 things most people will do - Safari and EE. either FP+ or early hours. again - common sense.
of course its easier said than done b/c i have been to disney - but still... its not that complicated in my opinion.