AT 33SA or OC9 for 1200 mk5

On Technics tonearm you’d better use MM cartridges with mid or high compliance with stock headshell. You can use MC, but try to avoid low compliance on this arm. It was made for MM cartridges and AT MM are great, don’t forget that you will have to re-tip MC cartridges, how can you do that ? Do you know the cost of re-tip at AT or elsewhere ? I’ve been using At ART2000 on my old Technics, nice cartridge, but i was blown away by AT-ML170 and AT-ML180 OCC MM series, they are more expensive than AT MC that you have mentioned.

One of the best cartridge for this tonearm is Stanton (and Pickering) from the golden era, upper model with Stereohedron styli, they are so sweet, i’m a big fan of them. They are not expensive and very nice for this tonearm/turntable. I have many different models, my favorite is CS100 WOS.

As you might know Kevin at KAB USA (who specialized in Technics service) always recommend Stanton/Pickering vintage models. In my opinion the lower models are nothing special, but top models are truly amazing. Read it and you will find AT-OC9 in this article too.

For MC cartridges you could change the arm for something better. 

Well, i’ve seen some people using even 32g SPU cartridge on Technics tonearm with a custom made superheavy ring added to the counterweight, but in my opinion this is a perversion. It’s like mounting a wagon on top of your sport car.

Technics tonearm designed for MM cartridges, check for the mass of this arm, it's relatively light mass, that was a 500$ turntable back then, if you never re-wired your Tonearm it is a bad idea to use MC cartridges on it. The weak part is some sort of a "motherboard" where the tonearm wires goes to, look here. It’s crazy that there is a weak connection between 5 thin wires from the tonearm and external rca phono cable. You do better get rid of this strange connection, you’d better solder some proper tonearm wires (like Cardas or Discovery) directly to the external phono cable (i like Zu AUdio Mission Phono) on this board, to avoid signal degradation. You have to use cardas soldering with silver.

A low output MC cartridge signal is very sensitive to cables, shielding and everything before the phono stage.

This problem is irrelevant for MM/MI cartridges.

The old Technics SL1200 mk5 is nowhere near the new SL1200GR, the tonearm on the old Techics is not as good as the new one.

For cartridges like ART-9 you definitely need a better tonearm, it is easy to replace the arm on your mk5.

BUT if you want to stick with the stock tonearm try to find some killer MM or MI cartridge like Grace, Victor, Audio-Technica, Grado, SoundSmith, Garrott, ADC TRX II, Stanton/Pickering ... There is nothing to lose for you in your setup between MM and MC.

BTW: Saec SS-300 mat is great for this deck! Isonoe footers are great, you can even buy KAB Fluid Damper for high compliance MM. Along with full rewire you will upgrade your mk5.

It is much better than to buy a LOMC and notice hum and phonostage problems later on.

That’s the benefit of AT’s MM product line, interchangeable stylus.

Definitely, but not only Audio-Technica.

Some manufacturers offered so many options to the customers:
For example Stanton/Pickering offered all types of styli for their MM to play not only microgroove stereo, but also mono and even different 78 rpm. And all these just with spare stylus, but with the same MM cartridge.

Another brand that did the same is Grace, they made all kind of styli (Conical, Elliptical, Unitily-4 (LineContact), Discrete-4 (Shibata), Luminal Trace, Micro Ridge) and nearly all kinds of cantilevers (Aluminum, Beryllium, Boron, Ruby, Sapphire and even Ceramic) ...

This is Audio-Technica MicroLine stylus, the benefit of this stylus is very long life span (1200hrs at least). This is the most resolving and accurate stylus. But apart from ML there are many similar under different names like MicroRidge, MicroReach, SAS, Repliacant 100, Gyger, VdH ....

Shibata is very good profile too, but again there are different names Stereohedron, FineLine, Vital, Micro Tracer ... depends on the manufacturer and patent.

The statement that one profile is more "musical" than another is false. There are good and bad profiles, some people like bad profiles and call them "musical" (a conical for example). The profile must have a wide contact groove area, so you can actually hear what’s on the record. With cheap profiles you can’t hear something, you lose frequency extensions (the wound is rolled -off). Cartridge signal generator, coil wire, magnet type ... everything important. 

There are many more very interesting cartridges in the world that AT or all the usual suspects. Do not stick to one brand if you want to try something interesting.

This combo tipped the scales at right about (IIRC) 19.7g and the stock counterweight could not level this out. I could have just gone with the 1.8-2.2g tracking force but wanted to be able to at least balance the assembly...

There is a stock subweight with every Technics SL1200 series, just screw it in. If you don’t have it you can buy here for $12.95. With subweight you can balance heavier cartridges/headshell.