Thank you @dfhaleycko for your helpful answer. It seems that one cannot go wrong with either preamp and it should be down to personal preferences (the reason for my question) and features. In that department ModWright has the edge I think with its mono switch and front panel settings; although for the moment I only have 1 arm/turntable so when it's set..it's set! Best sound reproduction is my priority, not features.
I was also intrigued by comments above about Herron sounding better through a SUT. I actually do have a very nice Rothwell MCL SUT (1:20) with Lundahl transformers which contributed very much in a better sound in my system, so I guess I think highly of transformers (ModWright again, although in another thread was mentioned that the 9.0 does not use one of Lundahl's best models).
And price-wise, a second-hand Herron is about $ 2800 shipped to Europe (where I live) vs 3400 for a brand new ModWright 9.0 and 3900 for a demo 9.0X upgraded unit. And cost is of course a factor...
To give a bit of a context, currently the SUT is fed by an Ortofon MC Windfeld cartridge mounted on a carbon fibre Pro-ject 9CC
Evo tonearm on a Pro-ject Xtension 9 Evolution turntable (current phono stage: Project Phono Box RS).
My setup sounds quite good, it's well balanced and I don't have
any real complaints. But, of course, I wonder what may I be missing
compared to a higher end phono pre ! My amp and speakers are also quite
good, revealing (detailed & transparent), tonally correct and natural-sounding, without being
warm or lean/harsh (30 Watt Class A Tube integrated Audiomat Aria
amplifier driving 2.5-way JMR Cantabile Suprême transmission line
floorstander speakers).
