The Herron is so much better its hard to believe. You will be amazed. I was shocked to discover the PH3 has a whole lot of tonal coloration. Its got a woody boxy sound. Doesn't sound that way now. Sounds great. I know. Loved mine to death. That's why it was so shocking to realize how colored it really is. But the Herron is not "neutral" in the sense a lot of people use it, which to me sounds more sterile than neutral. The Herron is not sterile, not analytical, just gives you what's coming off the table. Really dynamic, everything across the board just way way better. Frankly shocking to think the PH3SE was $2500 new back 20+ years ago and now for $3k or so you are in a whole higher level, and that's even more incredible considering how much inflation we've had in those 20 years. $2500 was a lot of money back in the 90's!
The Herron is also much higher build quality. Every single aspect of it is better, from the case and power switch to the inside build. Its also made to a much higher standard with things like a warm-up circuit that increases tube life by ramping up when turned on. Takes about 30 seconds to power up. Takes another 10 min or so to sound really fantastic. Although honestly if you listen to it without that 10 min you will probably not even notice, it sounds that good.
The power switch is on the back right, which might be awkward depending on your layout. Next to it on the back is another rocker this one to reverse AC phase. This actually does make a difference! Keith uses his infinite impedance design that sounds great. Any loading can be had with RCA plug swapped. Keith ships them with several loading options but you could solder any resistor in there and be able to change loading easily. Huge improvement over the PH3 that requires opening the case and soldering resistors.
About the only downside is the Herron does seem to be more sensitive to a perfect phono lead/cartridge connection. The PH3 is one of those nice easy phono stages that can be pretty much dead quiet pretty easily. When the same setup was plugged into the Herron it was quite a bit noisier, and I had to try several things to get it down, but honestly still not as quiet as the PH3 was. Several other people have said similar, so it seems to be just one of those things. Certainly there are phono stages that are even worse. In any case its not really the stage, because if you can track it down and get it right its freaking dead silent. I just have other priorities, especially when we are talking about a level that is only about the same or less than normal groove noise.
Main reason I mention it is so you know the Herron is so good you have to really start hunting to find anything even resembling a fault. Plus you get Keith Herron, one of the all-time best in the business. Keith is the exemplar of old school humility and respect. Customer service second to none. Many of us regard the Herron as a one and done. No further need to be looking. It is that good.