It's funny, I have never tried the hydrokinetic but I have Ron Toney's precursor that looks like a planer. Still works after all those years, used it on a flat sofa the other day. I like my pmf internal jet tools, especially for fine fabrics. I have the shear dry, Prochem tool and a couple of Kleenrites. I have used the Sapphire and like it better than the Shear dry. I'll have to try the hydrokinetic.
I tried the Hydro Kinetic and it does good on flat surfaces. The problem is upholstery has many curves and edges. The tool is real close to being great but they have too large of a glide which adds weight and makes it a little awkward.
The Sapphire is a great tool. Light weight and still gives you the "dry technology". You can clean safer, drier and with less fatigue.
The Sheer Dry is another cheap knockoff. If you can't afford the best or don't clean enough upholstery to know the difference, then maybe this is the tool for you. ???