Depends on the use case. If the grid's items have varying widths then masonry is the better option. However, for a grid with equal width items, I'll definitely go with magic grid. It's just so much lighter (2.3kb minified) than masonry (23.5kb minified).
I really don't see what's lacking with CSS Grids for equal-with items. Even accommodating different sizes, and allowing reordering for packing, works fine with just CSS.
Thanks. This answers the very question I was about to post.