All just my personal opinion
Beethoven: String Quartet op.18/4 — comparing recordings with the following ensembles: Amadeus Quartet (1961), Artemis Quartet (2008), Emerson String Quartet (1996), Endellion String Quartet (2006), Guarneri String Quartet (1995), Hagen Quartett (1999), Melos Quartett (1983), Quartetto Italiano (1975), Quatuor Mosaïques (2004)
Beethoven: String Quartet op.18/3 — comparing recordings with the following ensembles: Amadeus Quartet (1961), Artemis Quartet (2010), Emerson String Quartet (1996), Endellion String Quartet (2005), Guarneri String Quartet (1995), Hagen Quartett (2012), Melos Quartett (1983), Quartetto Italiano (1972), Quatuor Mosaïques (2005)
Beethoven: String Quartet op.18/2 — comparing recordings with the following ensembles: Amadeus Quartet (1961), Artemis Quartet (2002), Emerson String Quartet (1996), Endellion String Quartet (2008), Guarneri String Quartet (1995), Melos Quartett (1983), Quartetto Italiano (1975), Quatuor Mosaïques (2005)
Beethoven: String Quartet op.18/1 — comparing recordings with the following ensembles: Amadeus Quartet (1961), Artemis Quartet (2010), Emerson String Quartet (1996), Endellion String Quartet (2008), Guarneri String Quartet (1995), Hagen Quartett (2003), Melos Quartett (1983), Quartetto Italiano (1972), Quatuor Mosaïques (2004)
Mendelssohn violin concerto op.64: Comparing recordings with the following artists: Kreisler/Blech (1926), Mullova/Gardiner (2002), Tetzlaff/Järvi (2008)
Beethoven, “Eroica”-Variations op.35, Comparing recordings with the following artists: Artur Schnabel (1938), Glenn Gould (1970), Svjatoslav Richter (1970), Emil Gilels (1980), Konstantin Scherbakov (1984), Alfred Brendel (1985), Olli Mustonen (1993), Ronald Brautigam (2010)