How to choose a cartridge?

I have not heard the Audio Technica cartridge you are considering, but I have heard the top of the line ART 1000 and it is terrific and not as pricey as other top end cartridges; it makes me wonder if some of their other cartridges are also reasonably priced.

The thing about them that is not metric orientated is that the channel separation is not really indicative of a good cart.

I'd say that it's very hard to expand on the merits of a cartridge without considering the step up / phono stage. In my experience the cartridge - step up / phono  matching is just as, or even more important than the cartridge itself.

Try looking for people who have the same step up / phono as you do, and what were their experiences with these cartridges.

The only one I loosely know, was running the u-Benz LP S.

So I suggest that you upgrade your TT and your tonearm. Worked for me, but YMMV

Cool.
What did you upgrade to?

I am not sure what I would upgrade to, as I think I have a decent TT, arm ,and phono stage already.

So I cannot imagine any upgrade that could come to fruition without at least 5 digits of bills, and probably more like 20k+… and likely more than that.

No substitute for listening.   But I have to say I have bought all my carts 'blind'.

OP is correct.  Too many to listen to and dealers rightly don't like lending carts as once opened resale value slides right off the scale.

I have ART1000, Ortofons Anna, A90 and most recently Verismo, plus various top-end van den Huls.  Anna is lush, A90 pure and analytical, Verismo in between, tending towards A90 but quite a large improvement.  Don't write off the van den Huls.  They are a bit cheaper than other high-end and particularly low-cost to re-tip and overhaul.

@larryi yes the ART1000 is a really accurate cart, perhaps because of its unique suspension system that doesn't rely on the ubiquitous polymer grommet that can harden and degrade surprisingly fast.  But the Ortofons are emphatically NOT warm, I's surprised you find that and in any case that's a big generalisation on a company that makes dozens of models.

Don't forget that your choice of phono amp can vary the sound of a cart very significantly.  Unfortunately just another black hole because it's extremely difficult to try each cart with multiple choices of amp.  In my limited experience each cart definitely has a marriage made in heaven with one particular amp.  I last upgraded from an AR Phono 2.  I listened at home over three weeks to three contenders in the $15,000 range with my three top carts.  Very easy to switch carts on my Simon Yorke Aeroarm, an air bearing design where multiple carriages can be swapped in a couple of minutes, each holding a pre-aligned cart.  My choice overall was van den Hul The Grail SB that perhaps tends towards the accurate and analytical but certainly can play music.

I should have specified the Ortofon model—they were SPU models that were quite warm, while the Anna and PW are quite the opposite.

I don’t know if they still offer the service, but vdH use to allow buyers to break in the cartridge then send it back to the factory with a report on what they want changed about the sound; the suspension would then be tuned to try to meet the customer’s specific preference (the service is included in the purchase price).

No substitute for listening.   But I have to say I have bought all my carts 'blind'.

I love the mix of man-spraining with honesty, and I totally agree.
(so it brought quite the smile to my face)

But, alas, I am generally sequestered in the middle of a desert.

 I last upgraded from an AR Phono 2.  …

I upgraded from an AR PH2… which is likely about 30+ years old S/S MM stage.
It is not bad for what it is, and the upgrade is a better… just not like gates of heaven opening... better.

It is quite difficult to audition cartridges, particularly because they are in a system that is totally different from one's own.  I have a local dealer that will allow trusted customers to take home and try certain cartridges that are in the store, but that must be nerve-wracking for all concerned.  I think he even allowed someone to take home an ultra expensive Allaerte cartridge.  So, at best, one hears a cartridge or family of cartridges in familiar systems to get an idea about the sound; after that it is sort of a crap shoot and a matter of making other system adjustments to get the sound right.  

What is "right" might also depend on the music and one's mood.  The truly dedicated might actually swap cartridges or have multiple arms or tables.  I am not so dedicated to analogue, so I stick with one cartridge for a long time, even if I have two quite different sounding cartridges (Lyra Titan and Transfiguration Orpheus L). 

I think you have a very good analogue rig, so it certainly deserves a great cartridge.  At best I can only say I have heard, and liked cartridges from the following brands: Lyra, Dynavector, Audio Technica, Ortofon, Koetsu, Allaerte, and van den Hul.