I have the Tantus O2 Mark, and I love how it feels when I clench down in orgasm.
I have the Tantus O2 Adam & find it too firm for when I clench down. I do better with the VixSkin Bandit because I love the squishy outer layer. Both are way too girthy for my comfort! My problem is the core is still too firm for me, but better than anything I have tried thus far. If I could get a dildo made of only the outer material of the VixSkin, or maybe with much less of the core, I would be so stinking happy!
I love that they're soft enough for me to actually handle an average girth comfortably, since I'm on the small side (my VixSkin Tex and Mustang and O2 Mark are the biggest toys I can insert, and I love them!). It's nice to feel legitimately full without hurting myself. Dual density forever!