WHICH POWER CONDITIONER IS BETTER PASSIVE OR ACTIVE WITH ISOLATION TRANSFORMERS

I have used several of the PS Audio regenerators.  Everything except my subs is plugged into it.  Very satisfied with the results, especially when I come home and it has shut everything down and the series of lights on the unit tells me why.  Can't imagine ever living without one.

While there are numerous theoretical pros and cons to the design consideration of either a passive or active power conditioner, the manufacturers you list (AQ and Audience) have designed their equipment to mitigate negative effects and improve SQ.  Both use high quality parts with excellent mechanical design quality.  That said, and as you state, theoretically  active conditioning can reduce peak power delivery and introduce broad band noise. I would assume from the literature that is why Nagra has both active and passive circuits in their design.  Passive filtration theoretically can introduce resistance that limits instantaneous currents demand that impacts dynamics.  The best manufacturers have mitigated the risk.  For example, the Shuntata Denali has both low current and high current outlets, where the former for maximum noise filtration and the latter for maximum, instantaneous current demand.  On a side note, the Nagra has a “current reservoir” to provide for instantaneous current demand.  I cannot comment except I have also heard some say the Nagra limits dynamics in their opinion.  For those that recommend regeneration, theoretically it is the way to go if you are in an area with line voltage fluctuations, but if not, conditioning is the way to go IMHO.  For example, at my vaca home in Vermont with large voltage fluctuations its regeneration.  In my home in the suburbs of NY where mains line noise in this densely populated area is more of a problem, conditioning is the way to go.  So, in conclusion, and I know I will not really give you an answer:

1. The theoretical  pros and cons of passive vs active conditioning have been mitigated by reputable manufacturers like Audioquest, Audience, and Shunyata.   You cannot state factually one is better than the other.   It will come down to system integration and your perception of the improvements in SQ.  
2. If you are in an area with large mains voltage fluctuations, consider regeneration.  
3. While I personally prefer passive conditioning by Shunyata and Audience,  and have both in my system, it is my preference.  Please audition and make your own choice.  
   
   
    

Doesn’t any device that galvanically isolates the current prevent all noise?  That’s why so may manufacturers use galvanic isolation in their circuits to clean data feeds.  Seems to me that between galvanic isolation and the use of a filter and capacitor to ensure adequate current, you solve your problem-assuming you actually have a noise problem to begin with.  I’ve added DC filtering to my circuit because of all the digital equipment in my house and the neighborhood

I demoed and/or purchased a number of conditioners, regenerators over the years, Shunyata, Audience, PS Audio, Audioquest, I could see all being effective for some, so many variables to consider. For me BPT 3.5 Signature with custom Plitron transformer was the winner, further diy customization via film filtering caps and Oyaide R1 AC outlets. Always prefer amps straight into wall on dedicated 20amp, 10AWG dedicated circuit, this with anything from class a/b SS to 7wpc SET. transients always negatively affected by going through any of the pathways through conditioners, regenerators.

@langla4 Galvanic isolation is a type is active power conditioning as well as a safety circuit to prevents high current from flowing to sensitive components or prevent shock.  It uses electrical (isolation transformer) and physical isolation (gap) to assure the input and output is separated.  Passive power conditioning uses capacitors, inductors, and resistors to filter noise from the power without actively changing the signal rather than isolating circuits.  Theoretically, galvanic isolation prevents ground loops and potential differences between circuits by completely separating them, while passive power conditioning filters electrical noise on the mains (high-frequency disturbance).  So, application is similar to prevent noise, but slightly different as well.