Definitely the MiMi... it's cheaper and from what other people say, it's stronger than Alia.
Plus I think it's stronger than quite a few other small clit vibes I've tried, like the Leaf Life. I found MiMi to be much stronger than that. I also find it to be a bit stronger than the We-Vibe Salsa. Though the Salsa's vibrations are a bit deeper than the MiMi. If the Salsa had just one more higher steady vibration speed, I would say go for that (or the Tango) instead.