MiMi is one of the strongest vibrators I've found outside of wands/corded toys.
All the comparisons I've read say Siri is weaker, so I haven't looked at that one. Siri was on my list when I was looking for a first toy again, but I kept seeing references to it being weaker than others I was looking at so I put it to the side. Same with the Zini Seed.
I think a lot of it is personal preference and needs. MiMi is by no means diffuse (not like a wand or the Forbidden Fruit), but someone who wants very pinpoint would be better off with, say, the We-Vibe Salsa.
And I think people have the idea that "rumbly" in vibrations is "better". However, if someone prefers buzzy, MiMi might not feel right and they might prefer a weaker toy that has more "buzz" and feel it's stronger due to preference. When rating strength, I try to be unbiased and I rate by feel in the hand and then take shape and such into account.