Currently, you just show your hotel room key in the morning- I always thought that was dumb because you could just keep your hotel key and use it all year long if you're a local- but I digress.
So they'd have to do what, show your room key to get on a ride? I guess it wouldn't be that different than now.
This just goes to show you how much better Disney is with their infrastructure and MM+. The Room Key + Park Ticket + Express Pass + when I have Dining Plan Cards (that I buy in Sept for buy one get one half off)- it's just ridiculous.
I'd be fine with either. I like the morning now, because I have young kids that wake up- but it's still a bit early for them with the 1 hr time zone change. So each way would have it's benefits for me, personally. But for the majority of their demographic (older kiddos)- Id think night would be much more beneficial. And with the 5k extra rooms to be added in the next couple years- they might even be able to do them both. And at a reduced cost, even- just close an hour earlier and keep the last hour open for on-sites.