I have these decks since 1998 and it was my dj set-up for ages. All cartidges i have tried in the beggining were total crap in terms of sound (but it was very long time ago).
The best hi-end cartidges i have tried later and liked very much on this deck were:
1) MM Technics EPS-100cMK3
2) MM Technics EPS205cMK4 (both headshell integrated).
3) MM Denon DL-107 (with Orsonic headshell or Audiotechnica Magnesium headshel ala Technicard)
4) the winner: MC Audio-Technica ART-2000 (limited edition) - probably the best cartridge, sounds amazing even on cheap technics sl-1210 tonearm with Kab Fluid Damper.
After all upgrades i've done to my SL-1210 i have just bought another much better turntable and i'm more happier now with Technics SP-10 mk2 with Technics EPA-100 or Thomas Schick tonearms (on my plinth i can use "9, "10'5 or "12 arms easily). But it's not the end, so many thing to try ...