How to choose a cartridge?

I don't know if any particular measurement says anything about how a cartridge might sound, much less whether one will like that sound.  It might well be case, as some mastering engineers have said, that distortions and artifacts inherent to the making of records and extracting the information on records might be what attracts some people to record playing.  I suspect that this, at least in part true.

I once borrowed a table from a shop while mine was under repair.  I noticed that that this setup had a particularly expansive sound field that seems to envelope the room.  I had, at that time, a Yamaha DSP-1 processor that creates multichannel reverberant information to feed to side and back channel speakers.  One setting was essentially a Hafler circuit that extracts out of phase information from the two channels to feed to separate speakers.  When I engaged this circuit, I got a lot of out of phase information FROM A MONO RECORD (with my own table, I would get no signal when engaging this circuit when playing mono records).  The cartridge was not wired out of phase an there was enough in-phase information for there to be a proper center image and proper left and right instrument localization with stereo records.  The amount of out of phase information (i.e., distortion) was not enough to destroy stereo imaging and it may have actually been an enhancement, at least with some recordings.  

Dear @larryi  " I don't know if any particular measurement says anything about how a cartridge might sound, much less whether one will like that sound.  "

Rigth+.

R.

I don't know if any particular measurement says anything about how a cartridge might sound, much less whether one will like that sound.  

I think it was Lederman who said that the channel separation is a general sign of manufacturing quality. (Maybe it was in a video?)

Yes, good channel separation will tell you that the stylus is properly aligned with the signal generating elements, that the left and right elements are consistently made, etc., provided you make the measurement on the particular cartridge.  The manufacturer's specification or the measurement of a reviewer won't tell you anything about your cartridge.  Once you buy it, you are pretty much stuck with what you got, so, at best you can try to discern which builders have a reputation for reliability.  

I am getting an arm rest for the Schroder arm, from Galibier in Colorado.
It is coming together.