Questions to ask as I shop for a tonearm?


I’ll be upgrading in 6+ mos. I’m asking now because I’m still learning. I want to take plenty of time to understand the relevant technical aspects of something so complicated & what makes one person love brand X & another person dislike it.

I have a George Warren tt & a Sumiko Blackbird cart I’m waiting for to put on the stock Rega 250. I’m also waiting for Christmas to hookup a Jolida JD9 mkII.  My budget will be ~$1500. While brand & model suggestions are appreciated... I want to learn about tonearms. As always, I appreciate the knowledge you all pass on to me.
tochsii
Another Japanese arm to consider is the Fidelity Research FR 64 FX. On the heavy side, not really suitable for high-compliance carts, but a really great arm at the price.
Seconded on the FR64fx, if you're interested in moving to medium compliance MC carts. It's a phenomenal match for low-compliance carts like all Koetsus and the Red/Blue/Bronze in the Ortofon Cadenza line. It can also be a great match for many medium-compliance carts, which is most MC's. Great build quality and bearings. 
I like the FR64fx, but the price is way over $1500 budget considered by the OP 
That’s not my impression of 64fx pricing, given some patience. Now if you’re looking for a super-clean/mint example with box and all accessories and don’t want to wait for a hot deal, then sure it’s going to be north of 1500. These are quite old arms, and even though they hold up very well, the typical example shouldn’t be costing a fortune.

If you find a nice example without a headshell, then go for it. That's one premium you don't need to be paying; the FR headshells aren’t great anyways. Silver or copper wiring - both sound fine.
 the FR headshells aren’t great anyways.

There is a great FR headshell: model RS-141 is my favorite