I dug into this myself just now. At it's core, uMatrix is "default deny" so it doesn't need all the blacklists. But there are things that uBlock Origin provides that uMatrix does not perhaps including cosmetic filtering, popup blocker, zapper/picker element, etc. The author Raymond Hill (gorhill) has switched back to uMatrix himself and dedicates more development efforts to it now.

https://discourse.mozilla.org/t/support-umatrix/5131/179