I think the bookshelf is better especially when it's nearfield set up. It does not require a large volume and has the same horizontal orientation as MTM Center standing vertically.
I don't have bookshelves. When I use MTM center vertically, It seems to be a little better. But the speaker covers the screen, so it cannot be used for a long time. If I use MTM center horizontally, the soundstage is too narrow.
I used the 1961 monitor and center. The sound is fantastic. But as expected, MTM center is the biggest weakness. Even when I use it alone, it sounds better to turn off the center If I watch a musical movie.