Purifi v Gan amps?

compare Purifi based amps eg MarchP422, Purifi etc with Gan amps

Probably nothing, or everything. Audiophiles talk about synergy. This is where measurements help, rather than handwaving and guessing.

Ralph’s class D amps (Gan) have input of 100K ohms - this is good. They are only suitable for 60hz/120 V supplies. This makes them unsuitable for about 6 billion people.

The March amps (Purifi) have an input of just 20K ohms. This makes them unsuitable for many pre-amps which may have output impedances which may be nominally suitable at about 100 ohms or so, but at different frequencies they may be several thousand, so March is also unsuitable.

Its a waiting game for the designers to get their priorities in order.

In the middle are AGD (Gan) amps with a nominal impedance of 40K ohms, and with international electricity capability.

Ticks all my boxes, which I am a little bit sad about for reasons.

It’s pretty clear both technologies offer some high performance potential.  To me, I wouldn’t worry so much about the technology and just focus on whatever amp offers the sound characteristics you’re looking for. 

I know people who have been using  and building Class D amps for at  least a decade and they do not like the  sound of the Purifi modules.

Amps built with Purifi modules have no sound. 

With reference to my previous comments, they may be coupled with pre-amps or DACs that are unsuitable.  Like buying a car without a tow bar or is solar powered, there is no hope if you want to tow a trailer or a caravan or whatever.

It's all about the implementation, and all the other parts used.  Click on the dropdowns here and see how you can tailor Purifi sound.

https://vtvamplifier.com/product/vtv-amplifier-stereo-purifi-audio-1et400a-amplifier/