Having just changed my (and others) radius arm bushes here's a few observations for anyone considering poly bushes.
1, The yellow Britpart ones have a reputation to wearing out and turning to dust within a few months (no idea about the black or blue ones but I suspect they will be much the same as the yellow or orange ones).
2, My car was fitted with the supposedly far superior orange poly bushes (the ones that cost about 4 times the price of genuine original bushes). They've lasted quite a long time and many miles, but although the car didn't exhibit any of the usual complaints of wandering steering, vibrations or anything like that, it has always felt like the front tyre pressures were too high over small bumps and uneven surfaces even though the ride was fine on smooth surfaces. Having now changed to standard bushes, the steering is more responsive, the ride over uneven surfaces is vastly improved and the whole car feels much smoother.
3, The poly bushes are an absolute pain to remove. It took Marty's 20 ton press, a number of different sized mandrels, hacksaws, hole cutters and just about everything else we could find short of burning them out, to remove them from the radius arms. When we finally got them out, we found that they also allow moisture to get between the bush and the arm so rather than pushing the old ones out and finding a nice clean shiny hole, the inside of the radius arms were rusted to hell. It took a rotary wire brush to clean the surface, a punch and hammer to knock the rust scale off the inside of the radius arm and emery cloth to clean them up before they were smooth enough to press the new bushes in.
So the moral of this is poly bushes should be put into the same category as coil spring conversions, don't even consider them.