Both.
The OEM is more of a foam with some rubber like properties while the after market is far more rubber like. The OEM version compresses much much better...the door actaully fully closes without having slam it shut.
Adhesion was another issue. After pulling it off the door I could put it in a box and sell it as new...this after using the recommended 3M super black.
Interesting, there's a post over on the 40 section where someone else is running into this, but everyone prior had given rave reviews over his weather stripping - I wonder if something changed at his manufacturer. I'm sure even the rubber would compress and make closing the doors easier in the long run, but the adhesion thing is puzzling. I will say if the use a silicone mold release agent when forming the rubber, this can be a true nightmare to get off. I sell $70,000 IR Spectrometers to hose/gasket/O-ring makers to look for residual silicone for exactly this reason. You'd be surprised by how much cleaning doesn't remove, and how badly it can screw up adhesion of paints and glues. Usually an alcohol, something like ethanol/isopropanol will get enough of it off but it can take a couple of scrubs.