I have had both, different control arms and in different locations.
So far my personal experience has been that rubber is better.
It has more flex to it, when twisting, more forgivness. This seems to help prevent tearing and cracking.
My current control arms have poly busings in them. We replaced them about 2 months ago, have made three minor trail runs, and they are already busting out again.
I'm not a fan of poly bushings. When I get some extra cash, I'm going to put johnnie joints on the bushing ends of my control arms and be done with it altogether.
06 Rubi with some sort of double ended, chrome knobbed, cross threaded, infinitely adjustable, frequently breakable, worn out flammywhammers zip tied onto it.
It used to be a jeep thing... til that sh!t broke!