If you've had bad experiences with a Decca and a 309, just say so. Otherwise, your generalization is incorrect and a disservice.Please discount to recommendation to go to a Decca cart as they have a low compliance & require a heavy, (the heavier the better) weight arm.
If you've had bad experiences with a Decca and a 309, just say so. O
Never saw where a specific type of 3009 was mentioned, they range from 5g to 14 g effective mass depending
Here’s a great related site: http://www.analogue-classics.com/html/sme_3009___3012.html
VR
Andy
OP said he had a 309, not 3009. Effective mass =9.5 grams.

Was wondering about the Decca Gold hum you described, Grado’s hum on particular turntables, is there a correlation between them?
IME, Decca + Fosgate + Quads = Magic.
Since the Benz runs at 2.5 milivolts
Off I go to listen and tweak
Never tried a Grado, but from what I've read Grado Hum is from intereference from the TT motor and the cart - it tends to get a little louder as the tonearm moves closer to the motor. The Decca hum I'm getting is constant regardless of tonearm position.
The 33 series is said to sound a wee bit warmer than the OC9 series
Having used both for over 30+ years I would say that is correct.
That holds for the OC9 II, but the later versions are voiced with a fuller sound. OC9 III and the new XLS and XSH are not voiced as lean as the II series
I owned the AT33PTG/ii and now have the ATOC9XSL and the XSL is much more full and warmer than 33ptg/ii.Audio-Technica AT33PTG/II on a Well Tempered Classic V arm on my Sapphire.
The 33 series is said to sound a wee bit warmer than the OC9 series.
I would avoid Shibata tipped pickups from A-T. More expensive than MicroLine, more fuzzy to set up, faster wearing too.
So: get one like mine or the AT33EV version, or an OC9XML or OC9XEN.