I think there is a place in the current market for these MMJ reissues. If you compare an original (in good, mint or near-mint, condition) to one of these pressings, I think you'd be hard-pressed to find many differences in sonics. Van Gelder definitely liked the sound of stereo and did a great job mixing most of the 4000 series, after about 4020 and up. I wouldn't say that these MMJ pressings are meant to be an exact replica of the original, but are meant to fill a void in the market for a good, quality sounding Blue Note release... something we haven't had, on some releases, since the 70s with the Japanese Masterpiece Selection 150 series (pressed at King).
It would come down to personal preference on what YOU, as the listener, prefer to listen to. With a mint, first press, copy of Blue Train fetching five figures, you can pick up the entire MMJ set and more with that...
I, for one, find these MMJ reissues to be, what was once, a rare opportunity to own a clean-sounding copy of a Blue Note 4 and 5000 series release.