That's quite the list and a hard decision. I don't have, nor have come in contact with, the Mona 2, G-Ki, or Siri because they wouldn't be strong enough for me personally. I did have the medium Smart Wand (still have the large); it was about MiMi strength, but mine had a short and I sent it back and didn't want another. Wasn't all that great in my opinion. I do like the Eroscillator though. For me, it takes quite some time to get off with it most of the time, so I break it out when I want to take my time and when I want a different sensation (rubbing back and forth over vibrating). I'm a power queen and I thought it had quite a bit of kick, but again, it's moving back and forth, not vibrating. Also, it's SO QUIET, which I love (and need).
To be quite honest, I would recommend the Eroscillator (I have the other one, not the deluxe, because I didn't think the price warranted extra attachments that I wouldn't use), plus the soft finger attachment (and a very good quality lube, which you will NEED with the toy). But only go that route if you know that you'll like the oscillating.