No way does Midjourney do faces better than SD. I say this as someone who has used both extensively. I've used SD to fix the faces in some of my MJ images. I will say that SD sometimes does pretty bad at smaller/more distant faces in images, but up close it's amazing. You just have to use a decent model with it. Midjourney does have some strength over SD, though. It's very good at creating attractive images just as a default. You could type in absolute nonsense as a prompt and it would probably spit out something pretty.