Out of 3-4 recording of Bach's cello suites I own, Cassado's version may be the one I listen the most. I feel that it has the right balance between expression, speed, intonation, and also very reasonable technical audio quality, both the actual sound and the recording room acoustics. My favorites are Courante and Menuetto I/II from the suite 2 d-moll, but I like them all, every single minute on Cassado's CD's.
I also own Casals version (Opus Kura), Fournier (DG Archive) and Kirshbaum (Tetzlaff/Kirshbaum 4 CD EMI Classics ). Casals is off course excellent but the vintage recording noise can get in the way sometimes; Fournier has advantage of perfect sound recording quality but may have less expression then I'd sometimes welcome, or expression and speed that I find undesirable. However, they're really all great recordings and so it's hard to judge - apparently depends on one's taste and mood - but, if you don't have Cassado yet, it's worth to have a look at it. For record - I'm amateur listener.