Help me decide on my next cartridge (

So, we are talking about <$900.

Some fantastic MM or MC cartridges can be found for $900, not the Nagaoka, not the Ortofon, not the Grado, and not that Hanna MC and usual suspects. 

Actually for $900 you can easily look for best cantilevers, best diamonds, best generator etc. You can ignore all the cartridges with aluminum cantilever and conical/elliptical diamonds. Withing your budget you can pretend for Boron, Beryllium cantilevers with MicroRidge or LineContact diamonds if you willing to use your cartridge longer than others. You can find much better MM cartridge if you will look for top of the line models from the heyday of Moving Magnet technology (mid 70's or mid 80's). When you buy NOS (New Old Stock) you will get the best for the buck compared to modern cartridge. Some gently used also fine if you can trust the source. Stylus replacement is a benefit of MM, so i would not recommend to buy MC (especially refurbished or retipped). 

And yes, you can look for Audio-Technica, Victor, Grace to name a few of my favorite brands of Moving Magnet type. 

Cantilever type and mass is related to frequency response.
Stylus type is related to groove wear, sound quality and diamond life span.

Do not limit yourself with a choice of cartridges available in the shops today, we’re living in the digital era, there are much better cartridges produced in analog era (especially under $1k).

After reading many comments about serious problem with brand new Ortofon 2M cartridge pins (falling out when people trying to remove the lead wires) i can only think how poor is the quality control at the Ortofon today. I have never experienced anything like that even with 30 years old cartridges.