Clayton or Pass Class A, which one do you prefer and why ?

Neither. For my money I would much rather have an amp from CODA, Accuphase or Luxman. These amps have fantastic class “A” musicality, bass slam and very high quality parts make up.

Threshold and Plinius would also be on my short list. Take your time and read reviews. Many top choices are available currently.

For my money and maybe even yours I don't buy Japanese solid state. Nor did I say that I was going to buy either Clayton or Pass.
There are many who like both of them, though, and I am interested in their impressions.

@dill 

Clayton Audio not so much ....

As of a year ago, and currently to my knowledge, Wilson is still actively upgrading and repairing Clayton amps.  He upgraded mine.

Mitch is correct. Wilson Shen, owner of Clayton Audio, is now serving customers directly.  He can be reached at:

Clayton Audio
8151 Stratford Ave.
Clayton, MO 63105
TEL: 314. 862. 6017
email address: claytonamp@aol.com

I'd go with the Pass.

If you know anything about heat dissipation on heat sinks, the top mounted ones on some Clayton models are a not efficient at all for removing heat for Class-A heat dissipation.
You need vertical side mounted, and as many fins as possible. (thickness of fins are not important) surface area is.

I’ve made many very large pure Class-A amps >100w that heatsinks were not an option to use, as they would be as big as a coffee table.
I used a water cooled heat sink which was far better and cycled warmed coolant, through a slow fan cooled small radiator very effective but a very complex amp.

Cheers George