Juilliard String Quartet
"Bartok - String Qaurtets nos. 3 & 4 (Vinyl)

I have a recorded cycle of the Bartok quartets on CD also performed by the Juilliard Quartet made probably 20 years later.
Its amazing to think that when this cycle was recorded in the 1960's that some of these quartets were only 30 years old. It would have been interesting to observe audience reactions to Bartok's quartets when they hadn't been as canonized as now.

The middle quartets I think continue to be Bartok's most accessible as they are more rhythmically charged, more steeped in rustic folk music traditions and aren't overly lengthy.