Is it better to go up before or after dark?

Both try to get there just before the darkness you will see both

Go in the evening time...i.e just before dark so that you can enjoy both before dark view and after dark view as well. After dark your pictures won't be clear due to glass wall and reflection thing, but night view of city is amazing. Also day time view is mesmerising. So try both.

Before if its clear

Both

Before

It does look really nice at night too with all the city lights. I've gone both during the day and during the night. I have gone on zero visibility at night, and even then it's pretty good.

You can get a pass that allows you to go up at day then com back that night

I'd say before on a clear day. You can get a view of up to 4 states.