I voted for the server time based so I feel like I should explain why. The advent boss was a great little test of this and why it was better for me and why I feel like it is better for everyone(but not for everything understandably)
In my opinion it felt like there was less pressure to do things efficiently, I am a player with lots of time on my hands so making sure I get my digs etc on time is important so I can grow some money etc. For the advent, it felt much more free as there was a large time period in which I could battle him, as I knew it would reset the next day.
It felt better knowing I didnt have to run and battle him wherever I was. If I ran past hoenn then I could battle him and not worry about anything, as long as i battled him in this day then I knew I was fine. I think this more free and less time sensitive format is healthier and promotes more freedom, rather than people like me who could be worried with efficiency.