I didn't realize the ANA flight entailed an early morning arrival (in the back of my mind, I suppose I knew it did, but I tried to convince myself of otherwise). That definitely sours my opinion about it, but not enough to tip the scales in favor of MXP. That having been said, this might be a case in which I'd need to try out both in order to ascertain my true feelings. However, if the next morning's HND-BKK was an option, I'd switch to it in a heartbeat and make the most of my 20 hours in Tokyo (not full blown tourism, but definitely level up from the in terminal hotel idea). 20 hour layovers usually sit nicely with me as long as they're in places I enjoy, and Tokyo clears that bar.