Good thing about those rubber backed ones is that you dont have to trim them, they are perfectly clean and perfect when glued on place, they are not self adshive so glue is required, I have Scaleracecars ones and I am very happy with them.
Bad thing is that it is a bit tricky to detach them from that rubber thing and they are so small that you can lose them in no time.
But if you ask me that are the only ones I want to use, those regular PE parts (without rubber back) are extrimly hard to trim.