Class A preamp or Class A amp

"On the other hand" class "A" and class "B" may refer to two completely different things:
Class A class B refering to mode of operation IN class A (full signal always on) or class B 1/2 wave signal with switching)
OR.....
Class "A" as in Stereophile ratings: class A... class B etc.
The mode of operation is less important than how well it is implemented, so no real answer there...
As far as the rating sort of class...
A better pre or a better amp? that is open to debate, but I personally would opt for a better pre than amp. if I had to choose in that manner.

Thanks for your responses. As for Elizabeth, I was talking about the mode of operation. I have read that Class B or even AB has switching distortion in the transistor. In contrast, I have read that a well-built Class B can have two halves of the audio signal almost perfectly match just like it was operating in Class A.

The only class B stuff with "high end" aspirations I know of is Naim. Not my cup of tea.

Remember that class A runs very hot.
And that most amps running in so called class A really run in class A only up to so many watts, when they glide into class AB.
A "pure" class A preamp is pretty common, and you have a lot of choices... because that is where it really counts, in the low-level signals
So I would say the preamp class A

Transistors need enough bias current to 'Wake them up' into their linear operating range. Higher bias levels will generate more heat and use more electricity. Since heat is the enemy of long life a cooler design may be wise.
Ron-C