Park hours were more than adequate for us (we never spent evenings at the parks with the kids, except for the Halloween party one night and MGM another, when MGM had Fantasmic at 7 pm--at the close of regular park hours).
It was VERY hot the week we were there, I think it ran 5-7 degrees hotter than the "average" temps for that time of year.
MK closed at 9 each night we were there, except for the party nights when they were opened til 12.
I've not got much to compare to, since the last time we were at WDW was in 1992....but it seemed more crowded than we had expected during the time we were there. The day before we checked in was the last day to check in and still get free dining, plus it was a long weekend, with Columbus day the Mon after we arrived, and, I heard that local school kids were on vacation during part of the time we were there. All of these things could have contributed to higher than expected crowd levels. AND the food and wine fest was on at Epcot.
I have a friend who went end of August last year and she said the parks seemed empty...........Mind you, the parks were not packed when we were there, but I don't think we'll choose that time of year again, and I'll be more aware that a long weekend in the mix of my plans could alter park crowds, and probably do my best to check if local schools have vacation days during the time I do plan to go! For US, the biggest factor was the heat, it was DD10's wishtrip she had granted, and she does not tolerate heat well, we should have waited until November to go and would have been more assured of getting cooler weather.
I'm sure either time you go will be great!