GP was, well, fresh, while MM read more or less like stabled together from drafts for GP. It was basically the same story in green just not as memorizable as GP. GP had many little moment you remember, MM...yes, there was the bit with the sex toys and possible the golems, but MM leaves one (YMMV, of course) with a feeling that something happened without happening... It's there and that's it, but how everything goes together is...hard to tell.
As for Last Continent:
UA gives us several information about the daily life at the university that directly contradict information in Last Continent (wizards sleeping habits, for example) That wouldn't matter if it, in a way, wouldn't have been so essential in TLC that wizards don't have mealtimes between supper and breakfast. It's all just speculation and yes, a bit of overanalysis, but here's my string of thoughts:
In TLC the wizards order food out of the regular times in a greater amount than the 'occassional nightsnack'. Food which has to be brought to the study. Which then leads to the wizards getting stuck on mono island.
Now, if there'd been a nightkitchen and regular meals at 3 am (or it be at leats common for wizards to be up at that time, as it is in UA) they very likely would have brought food with them directly.
So, no need for Mrs Whitlow to come to the study and cause the following events.
As said, it is just speculation.