Tonearm comparison, Rega vs Zeta, anyone?

I forgot to mention, the RB300 I had was mounted on an Oracle — not the Delphi but the Alexandria, a step down but using exactly the same design principles (suspension, platter/bearing/motor, etc). All the other arms I mentioned above were mounted to that Oracle, and Rega was runner-up for last place. If you liked the Pirelli analogy, this may strike a chord — Putting a RB300 on a Delphi is like using Chevy parts on your Porsche.

Bimasta,
on some points we agree, others ..... well.

I’ve had the RB300 on the Delphi for 4-5 years now, & there’s a number of things I like about it.

The tonearm I had be for the Rega was a Syrinx LE1. I used it in conjuction with a MM Grace F9 from 1984-2012.

Never really like the Syrinx for various reasons, but set up properly it did sound good.

As for comparing the two set-ups (Old): Syrinx LE1. MM Grace F9.
(Current): Rega RB300. Grado Reference Sonata1.
(Next Week): Rega RB300. Dynavector 20X2.

I never found the Syrinx sounded any better than the Rega .... but I prefered the Grace.

Never  Heard a Zeta but chalk me up as another rega hater.  Always found the hype to far surpass reality in my opinion. 

Just a thought. The high mass Zeta may be a bit heavy for the Dyna 20, but the SME M2-9 would be a nice step up from the Rega, a good match for the cartridge from an effective mass standpoint and SME arms were commonly bundled with Oracles and are part of the design center of the turntable.

The Syrinx LE1 was the bottom of the Syrinx line, their offering in the "budget" arena, and unlike Rega they weren't geared up to mass-produce, crucial in that low-margin market. Quality control was all over the place.
I have and still use the better Syrinx PU3 and it's superb. It beat the SME 309 (IME) — the 309 is a pricey high-end arm — in a strict head-to-head comparison. And I didn't want it to, so there was no confirmation bias. It destroyed the RB300.
I've not heard the Zeta, but it was reputed to be competitive with the PU3, one the "super arms" UK seemed to produce in abundance during vinyl's so-called Golden Age.
Viridian's suggestion is a very good one, and he notes the Oracle/SME connection. SME made an arm specially for Oracle, though it was a variant of their TOTL V, as is the 309. Again, I've not heard the M2-9 but I've owned several SME arms and they never disappoint.