The Belcea Quartet are truly excellent in the six Bartok String Quartets. Precise, but not too much so (as with the Emersons, whose DG recording is, alas, over-rated in my opinion), but with a hefty dose of local flavour.
Having said that, there are many superlative sets of these works, works which repay repeated hearings as well as anything, and are on a level with the Beethoven quartets. Alternative recordings equally worth considering include the Tokyo (DG), the Takacs (Decca, but also their earlier Hungaroton recording, albeit with a different line-up), the Vegh (Naive), the Keller (Warner), and the Vermeer (Naxos).
This cycle is up there with the very best, and I say this despite having approached it with a foolish prejudice, that such a young group couldn't get to the very heart of this great music. How wrong one can be!