RPM's are most definitely better as they "snap" on tighter and are more resistant to popping off or distorting in the advent of a crash. My personal experience is that the Black RPM's have always worked great while the blue or neon yellow ones have been hit or miss over the years to where I only run black RPM's.
I put AE cups on my pan car and I find they pop off really easily. I was shocked that even with new pivot balls there was still slop in the steering. Ended up having to put o-rings under the ball-cups.
I'd say go RPM. Better but more expensive - worth it.