I tried all four devices you asked to compare. In terms of accuracy -and responsiveness- Headmaster and Headmouse Extreme are the best. Nothing beat them, they are just perfect like a standard mouse is. If you have a good head movement you'll take the best from them.
I'm a quadriplegia C4-C5 and I design with an Headmouse Extreme with sip/puff and the standard windows -or linux- onscreen keyboard. Inkscape, Illustrator, Photoshop, 3dsmax, Coreldraw, whatever software I try it works perfect. Occasionally I do simple video and audio editing. I have a two monitor configuration, sip and puff system is arm mounted on desktop, I use two reflective dots -to improve efficency- on the right side of my glasses, I can send photoes if you want. I can move the cursor all over the lengh of both monitor, from left to right and vice versa; if the headmouse looses the signal before acclompishing this task, I slighty switch back with my head, Headmouse re-finds dot signal and I finish that cursor movement. Headmaster doesn't have this little drawback -very little, You'll not ping pong your cursor all the time-; I felt uncomfortable wearing HMaster headset, it's also wired to the PC so you are not free to go away with your wheelchair. A simple dot on a comfortable support is the easyest option. Maybe in the future a lightweight wireless ultrasonic device will give a reborn to HMaster. Every InfraRed based device -SmartNav, Tracker, Headmouse- suffers from direct sunlight, but your display watching experience does it too, so You will ever not be in direct sunlight.
Today I also tried QUHA ZONO gyroscopic device, I was very attracted by this device: wireless and indipendent, enough lightweight, easily portable, can be used outdoor with smartphones etc.. I had to say that I couldnt try it in the best conditions and that I was looking for something performing like my headmouse. And in fact ZONO is something else. I need an easily portable -not to be used outdoor- and I'll go with an Headmouse Nano. I'll give another try to ZONO, but his gyroscoopic ancestor boost tracer seemed to suffer of the same 'kinda floating cursor' behaviour.
When I tried TrackerPro it was a bit slower than HMouse, it gave me back a light delay between my head movement and the cursor one. SmartNav is much slower so it gives a bigger delay.