All just my personal opinion
Franz Schubert, String Quartet No.15 in G major, D.887 (op.116): a comparison of 3 recordings, with the Melos Quartett Stuttgart (1978), the Emerson String Quartet (1998), and the Artemis Quartet (2009)
Beethoven: String Quartet op.135 —comparing recordings with the following ensembles: Alban Berg Quartett (1982), Amadeus Quartet (1963), Artemis Quartet (2011), Busch Quartet (1935), Emerson String Quartet (1997), Endellion String Quartet (2005), Guarneri String Quartet (1969), Hagen Quartett (1990), Hagen Quartett (2012), LaSalle Quartet (1976), Leipziger Streichquartett (1998), Melos Quartett (1984), Quartetto Italiano (1968), Takács Quartet (2004)
Beethoven: String Quartet after the Piano Sonata op.14/1 — comparing recordings with the following ensembles: Artemis Quartet (2011), Endellion String Quartet (2008), Melos Quartett (1984)
Beethoven: Great Fugue op.133 — comparing recordings with the following ensembles: Alban Berg Quartett (1983), Amadeus Quartet (1962), Artemis Quartet (2011), Busch Chamber Players (1941), Emerson String Quartet (1997), Endellion String Quartet (2006), Guarneri String Quartet (1969), Hagen Quartett (2001), LaSalle Quartet (1972), Leipziger Streichquartett (2006), Melos Quartett (1984), Otto Klemperer/Philharmonia Orchestra (1956), Quartetto Italiano (1969), Quatuor Mosaïques (2016), Takács Quartet (2004)
Beethoven: String Quartet op.132 — comparing recordings with the following ensembles: Alban Berg Quartett (1984), Amadeus Quartet (1962), Artemis Quartet (1998), Busch Quartet (1937), Emerson String Quartet (1997), Endellion String Quartet (2005), Guarneri String Quartet (1969), Hagen Quartett (2003), LaSalle Quartet (1973), Leipziger Streichquartett (2001), Melos Quartett (1985), Quartetto Italiano (1967), Takács Quartet (2004)
Beethoven: String Quartet op.131 — comparing recordings with the following ensembles: Alban Berg Quartett (1984), Amadeus Quartet (1963), Artemis Quartet (2002), Brooklyn Rider (2011), Busch Quartet (1936), Emerson String Quartet (1997), Endellion String Quartet (2005), Guarneri String Quartet (1969), Hagen Quartett (1999), LaSalle Quartet (1977), Leipziger Streichquartett (1994), Melos Quartett (1985), Quartetto Italiano (1969), Takács Quartet (2004)