I have Gigi which is similar to Liv and Uma. Gigi is okay, but only because of the shape. The vibrations just aren't for me. Liv's shape looks kinda boring to me. Add that to meh vibrations and I'm just not at all interested in Liv. Uma, on the other hand, is very strong. It's also waterproof, a major plus. Uma has a nicer shape than Liv, though it doesn't hit my G spot.
I actually like my G-Ki more than my Uma, even though it's much weaker. It hits my G spot and that makes me happy. I also think the Vr8 and Vr9 are better than all of the listed ones because of the vibrations, even if they also don't hit my G spot.