Used Navik is one choice. Lots around with broken missing plastic parts which Plastimo no longer sell. But spares are available from Mr Vee who also does a new and improved version.
Sea Feather seems to be eclipsing the others, the lightest for a small yacht, the latest design, .. made in Devon, still there now, and you can speak to someone in the workshop. No connection, except a lucky owner. But there's a waiting list...
Interesting hybrid with the Mr Vee USD vane on the Navik base. Both are remarkably lightweight systems so that should give the best of both worlds. Worth noting that the Navik is unique among production systems in that the wind vane actuates a trim tab rather than being directly linked to the pendulum blade, thus significantly reducing the load to be driven by the wind vane and the loading of all the moving parts, bearings, etc on that side of the system.
If that doesn't appeal, then on purely engineering design considerations the Seafeather must surely be the hands down winner?
When I put mine on, the Sea Feather brackets and fixings were part of the vane, whereas the Pacific Light needed a bracket making up. The overall difference in cost between each installation was pretty small. Sea Feather has a line to alter the heading so can be done from the confines of the cabin, and the Windpilot did not (so altering the heading meant dangling over the stern), but I think that this may have changed. The Sea Feather is British. There are rather more Windpilots around. Both Paul (Sea Feather) and Peter (Windpilot) were very helpful. Either would be a good choice.