one of the benefits of Polyurethane over rubber, is that Poly doesn't suffer the same compression memory as rubber, so holds it's condition and position much better. Some OE bushes are way too soft and compliant to start with, never mind when they've been in there a while.
'909' bushes, assuming they are made of similar materials to the older '905' Rallye Sport bushes, are made of rubber material, just a harder grade, so start off better than OE but degrade faster than Polys will..