Poly always has the chance of squeaking, whether due to climate or installation problems. Our bushings are designed to reduce squeaking - they are made of the same graphite-impregnated urethane material as Energy, but they have grooves in the surface to help reduce sqeaking (to the best of my knowledge, Energy does not offer this feature).
Poly is a great compromise between price and performance. Rubber is cheaper, but doesn't perform as well. Delrin/aluminum bushings have the best performance, but have the harshest ride and are the most expensive.
We've had some backorder situations before and our customer service suffered. The poly stuff goes out of stock from time to time, but our idler arms, center links, ball joints, tie rod ends, etc, are always in stock.
Rustic makes a good product for a good price. We charge a little higher but offer what we believe is the highest quality stuff out there.
I hope this clears things up - good luck with your rebuild!