The difference in sound between Birbigham and Berlin recordings must be that of the halls.
As for the Brahms cycle: I already said that I find the sound splendit, BUT in Japanese pressings. I don't know the Europian release but imagine that will be mediocre in the best case.
In Japan release the sound is full, warm, immediate, without glare in strings. I listen at full volume without the least discomfort. This is not the "audiophile" sound of Telarc, Exton, xrcd etc. and I find this much more good. You concertrate totally to the glorious music.
And you have the fantastic bonus of the 2dvds with all the symphonies.