Tantus tends to be mid-firm for most of their toys, although they do have several different silicones they use with different stiffnesses (per Metis they have three, not counting the O2 outside).

Vixen seems to have the softest regular silicone out there, Tantus and Fun Factory seem to overlap at the midrange with the stiffer Tantus being stiffer than Fun Factory. Ophoria is the stiffest general silicone, although the absolute stiffest I have ever found is the Evolved Talon.

I actually didn't find the Vamp to be really squishy at all; I thought it was pretty mid-firm. It had some definite give, and it was flexible, but not squishy.

Re: ScottA's analysis, I have to say that, yeah, Ophoria has really firm silicone, and Happy Valley silicone is just a tad below that. (Note: I only have one HV dildo, and it's pretty hard.)

The firmness is also related to design. I was very surprised when Metis said that the A-Bomb (which seems very hard) was not made out of their stiffest silicone.

Squishy works just fine. In my mind, "squish" is the response of the silicone to if you hold it in your hand and squeeze. "Bendiness" or "floppiness" would relate to how easy it is to bend the dildo, and "give" could be either.