I bed them all. No matter how good the base is the receiver top will vary in production rifles.
But to answer your question directly. I have found Near Mfg. rails to be of the highest quality for fit. I also feel Nightforce rails fit very well too.
I want to add, I have tested many rails and rings. I have seen many less expensive offerings fail. I set everything up using a straight edge, and centering points. Before I put a scope on I know it will have no induced stress on the tube from misalignment. When you start looking close you start to see where some fall short. This is for sure an area where you get what you pay for. And at long distances it shows up.
Jeff