Advantages of the big three fabric systems.....
Polytone has none, they were the best in the business 30 years ago. but no longer, their products are expensive, thinner now is $80 per gallon top coats are beyond that. see
http://www.aircraftspruce.com/menus/cs/index.html for price lists.
Stewarts, cleans up with soap and water, their primer for metal works great and any portion you don't spray goes back in the can. Big advantage no waste.
Their Eco-Fill (the primer fabric filler) rolls, brushes or sprays easy and cleans up with soap and water.
Their top coats are not as easy to get a great finish as the other 2 competitors, but it can be done.
Big advantage with the Stewarts is no thinners or clean up agents (Cuts costs) and they do not stink, as the other two competitors.
Disadvantages of the big three.
Stewarts, You must learn to paint all over again, it requires many coats to fill the weave, and it lends its self to orange peel if you don't spray it correctly.
PolyFiber, it is the most expensive of the systems, requires a thinner for clean up, and requires many coats of three products, (Poly brush/tack) silver and a top coat. plus it is the heaviest of the three.
Airtech, requires a thinner but cleans up with acetone, the top coat has a problem with contaminates in the paint, it requires a hardener and an a accelerator, thinner and double filtration before you spray.