What kind of driving do you do? Is it a fire road slow Off-Road toy, street and show, daily driver or hard-core off road beast. The Polyurethane will do well for all, just make sure you grease them when you put them on or they will squeak. If you want to save a buck, rubber will work, but you will need to replace them more often depending on how ruff you drive. Then like mine, it is a hardcore Off-Road toy that normally gets trailered to the desert and sand dunes. I was trashing Polyurethane and they lasted maybe a year before I saw them start to show fatigue. So I went with Delrin bushings. They are much stronger and are impregnated with oil for self lubrication. They worked great, but I went with a long travel coilover suspension and now run heim joints and the radius arms are custom and welded to Dana 44 TTB front axle housings. Also the front pivot bushings were replaced with 7/8" uniball's. I still run Delrin bushings on the rear leaf springs and work great until I makeup my mind to link the rear. Probably after I wear out or break the leafs.
Again, mine is basically a Prerunner toy for the dunes, a Go Fast Bronco.
The Polyurethane are probably your best option.
That is just my opinion and opinions are like farts, some stink and some don't.
David