Nice to see you being so active on the forums lately - I like the enthusiasm!
Of those three systems, I've used the worm drive and linear actuator. Both these systems do what they're supposed to do - track/redirect sun. But there are strengths and weaknesses to both.
Linear actuators - The best thing about this setup is the relatively cheap, readily available parts you need to build it. Once all the bugs are figured out - its a fairly robust system. But setting it up can be a pain - the measurements have to be dead on and there's a lot of re-adjusting. It also has limited range, which is my biggest problem with the setup. Can be a little noisier than worm gears - I apply oil to the lead screws periodically.
Worm gear systems are tougher to find, and way more expensive than linear acutator systems. On the plus side, setup is way more simplified, movements are quicker and there is no limit to the range that it can track. I managed to salvage and modify two worm drives from an old electric wheelchair and they work really well. Worm gears are also self locking, so you don't have to worry as much about misalignment due to high winds. And mine are in a sealed unit, so it's really quiet and can handle the weather.
Belt n pulley I've never tried, but I'd be a little concerned about the holding power of such a system in high winds since it's not going to self lock, and you cant depend on the holding torque of the stepper, which is powered down between moves with Gabriel's program to save power.
The big companies use slewing drives, which would, in an ideal world,what I would use. Basically, they're large self contained worm drives that can take alot of weight.
Winner in my books? By far a worm gear setup. Nicer to look at, easier to set up, quiet, efficient movement, gears are self contained and protected from elements, self locking.