I haven't been in the performance loop for quite a while, but your going to want to be looking at who makes the IC, not the packaged thing.
Asking for what company makes the best RAM is like asking which website sells the best processor. The actual question you would want to ask in this scenario would be what the best processor is.
I know Elpida used to make the fastest DDR3 despite being plagued with problems. This was a couple of years ago and the IC's in question have been pulled from the marked because of said problems. XS might be the best place to start your search for the best RAM ICs.