Big difference to me. Baby was not a juggernaut charging outrageous prices and American Buffalo was never going to really catch on and run long. It was (and is) too dark a play to attract a large Broadway audience.
The Barrymore was a plum theatre, Baby was a musical that would benefit more from the location and lack of a second balcony. I think they were trying to give Baby as much chance as they could. (I actually saw both shows at the Barrymore and thought it really was perfect for Baby). Also, since shows did move more in those days than now, I have to assume that it was a lot cheaper to move a show, especially one like AB (one set, three person cast) than it is today.
Beetlejuice (which right now I still have no interest in seeing, so I have no agenda), represents a huge investment and appears to be that rare case of a show that slowly catches on (and could have a decent run (beyond 6 months) as long as there are summer vacation, Christmas, Thanksgiving, Easter and Spring Break weeks to offset mediocre weeks (that I imagine are still currently making their nut).
In some ways -- and I am not complaining -- I think the real issue is with all these long runs that essentially have taken shows out of commission for decades. It makes the list of available theatres much smaller than it probably ever has been.
Ironically, assuming that Rudin does not really try to go for a long run after Jackman leaves (as was the case with Dolly) AND every seat will be sold for the entire duration of Jackman's run, no matter where it is), it seems to me that a perfect theatre for MM from the producer's perspective would be the Marquis...more seats, great location, no fear that the barn won't sell out). But he does seem to be very loyal to the Shuberts.
I would not be surprised -- if WSS is not a success -- if we eventually get an announcement that MM is opening at the Broadway. It could definitely gross more at the Broadway, provides a better opportunity to have some decently priced tickets in the rear-mezz.
For that to be possible, Beetlejuice can't lose steam and WSS has to flop. I personally am hoping that WSS is a huge success, as I am so sick of WSS productions that simply recreate the original production. It really needs a breathe of fresh air. If it does flop, though, the above would be reasonable.
Finally, if BJ is able to maintain its momentum and MM still wants the Winter Garden, maybe the Shuberts will consider underwriting the cost of the move. That is not something that I imagine anyone would consider this early, however. The Broadway IS occupied and who knows what other musicals will be lining up to open in the fall of 2020; they are not going to subsidize anything if there is competition for the theatre. The other problem of course is that, since it has already been opened 8 months or so, the probability is that BJ is not going to ever be more than a show that makes its nut X weeks a year and does great business when families are buying tickets. If that proves to be the case, it is never going to return its investment anyway.