Definitely do night so you can appreciate everything with the lights and atmosphere.
I did the daytime and it was fantastic- but only because I couldn't get seating for the night. It was our first time and loved it regardless.
I can see how the night is better, however tickets are tough to come by. We went during the day and it was great. Nighttime is harder to get tickets for and rough on the little ones I would recommend going first class. Nicer seating makes a difference.
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