I never heard them live. Martha Argerich is still performing live but it is imposable to catch her as she cancels whatever she can cancel. The Beethoven’s Cello Sonata are “big” and as many other thing many different people plays them differently. I do not think that there are “best” of them….

The Argerich always was strange. She of could a phenomenal performer but she quite frequency was unnecessary overly expressive, almost up to the point of being showy. If you like Beethoven’s Cello Sonata then sometime try other people play them. Try for instance:

Richter and Rostropovich
Du Pre and Bareboim
Fournier and Kempff or Schnabel or Gulda
Casals and  Serkin or Horszowski
Starker and  Sebok
Bylsma and Bilson

There are many sounds of the Beethoven’s Cello sounds… It well worth to find many of it’s reflections…