With respect to some who are well-known experts here, I don’t agree with much of the above. Except Lewm.
Peter Lederman of SoundSmith gives a very good discussion of this topic. My interpretation and memory of what he said, follows. Hope I got it right - you can check it.
He points out that crosstalk is partially a measure of how well the stylus sits in the groove, and that high end cartridges can have very different left and right crosstalk figures. He points out that it is better to have high thirties in one channel and low forties in the other, rather than high thirties in both. And that high end manufacturers do that.
My higher end Koetsu had to be canted at a terrible angle to achieve equality at 38 dB (Foz). An electron microscope photomicrograph showed that the stylus was perfectly symmetrical, so that was not the issue. The issue was, obviously, that Peter was right, and equalizing crosstalk was a big mistake for high end cartridges.
So I start visually by assuming that a high end cartridge isn’t too far off, and adjusting by ear. It’s not as fast or easy or repeatable, but after many small adjustments over a month, it’s pretty damned accurate.
That’s judged subjectively by how well the stylus sits in the groove and pleases the ear, as well as objectively by near perfectly symmetrical wear patterns on the stylus (photomicrograph).
My $0.02. YMMV
