The West End theatres receive some or all governmental funding. Whereas Broadway theatres do not. They rely on private funding. The London production is the original production. As that is where Andrew Lloyd Webber and his then wife, Sarah Brightman, (original Christine) live and work, Webber likely put more of his own money into that production to make it as lavish as possible. So, that could be likely why that production got better equipment and subsequent maintenance through the decades.
Phantom has been at the Majestic Theatre on Broadway since the beginning, 33 years ago. (Some shows move over a period of time, as audience size diminishes and to keep costs down.) As it is considered a show only tourists go to, (no huge celebrities now,) I doubt that it has the maintenance level of newer shows.
It reminds me of when I went to see the movie
Bohemian Rhapsody a couple of years ago. I hadn't gone to a movie theatre in ages. Prices too high here at $17 per ticket - and that's without popcorn or drinks. I went to an older theatre, known in the past to be more of an artistic theatre, where they show more independent, cultural art films.
I thought, therefore, they'd have the best equipment to see the movie. Instead, I was really disappointed that movie technology hadn't developed very much through the decades.

I could have sworn the last movie I saw in another movie theatre even had better screen quality. My old TV had a better high-def picture than the movie screen. And I thought the sound quality was kind of muffled and very flat sounding.
But, I loved the movie and am quite a Queen fan. So, I went to see the movie again, in a different theatre closer to home. But, one I thought would be a worse theatre, as it was a
movie theatre basically tossed into the Broadway theatre district. The company wouldn't spend much money on that, right? So, I thought.
Instead, the Regal Theatres at 42nd St has the most advanced, state of the art equipment that's out now. Each theatre is sized smaller, more intimate but still has a huge size screen. They have those automated lounger chairs. The image quality blew me away. (And it wasn't a 3-D version.) Yet, it was beyond high-def, with 4DX technology I know nothing about. Colors were so saturated and vibrant. I could see the pores on actors faces. And the crystal clear sound quality blew me away. It was as though I was actually live in Wembley Stadium during one of the most iconic music concert moments in history.

(I can't wait to see Top Gun 2 whenever it finally gets released. THIS is the theatre I'm going to.) This is how seeing a movie should be. But not every movie theatre (or Broadway theatre) has the funds to keep up the equipment or production levels so high.