having been to both concerts, both performances are special in their own way.
The Friday night concert, the atmosphere was insane. Alot of people complain about how long it was, how things were not right etc but that just added to the special, incredible, just indescribable uniqueness of what we experienced. Some memories like Michael onstage doing vocal exerciser during a break in performances or the fact that for a few years, before YouTube existed and became mainstream, we were the only ones who had seen Britneys performance. All the parts in between the performances which are cut out of the videos and TV broadcasts, we soaked it all up.
Just being able to watch Michael watch a show with his family and then actually go onstage and give the performances he did, never mind all the other stuff, seeing the behind the scenes stuff, just being able to watch him for hours and hours, it was time suspended.
Side note, the reason there is a different dancer on Monday night is because of Britneys contract. She could only perform once, as long as her performance was not broadcast. If her contract had been different she would have done Monday night too. Some of the performers did both nights,Usher was definitely on both nights, and Elizabeth Talyor. Honestly I dont remember much of the performers from the first night as me and my friends were watching Michael when he was sat in the audience watching the show.
Monday night show was also special and amazing and the atmosphere had a different intensity. New York was buzzing with Michael Mania, those who had not been to the Friday show experiencing something for the first time, those that had been to the Friday show getting to experience everything all over again. Ticket demand for Monday night was insane. Everyone who was anyone in New York just HAD to be there on Monday night, no matter the cost.
Mondays concert was just incredible, to see everything again, just made the atmosphere even more intense if that was possible. To have the luxury of knowing we would see Billie Jean again, Beat It again, The Way You Make Me Feel Again, sitting the audience watching Michael talk to Elizabeth and just knowing that in an hour or so he would be onstage was something so so special.
So really you cant say one TWYMMF was "better" than the other, as each need to be viewed in context of that particular concert.