All Tube vs. Hybrid Preamplifier

A quick browse of the tube preamplifiers for sale will bring up preamps with only two tubes to those with six. So, what are the pros/cons of going all tube (including rectifiers) vs. hybrid? What are the pros/cons of a single gain stage vs. two? I realize that generalizations are just that, and implementation is probably more important; but can any generalizations be made regarding this?

I don't think generalizations can be applied here; but others may disagree. It is my opinion that design , part quality selection and execution is what is most important. And in the end it is all about music and what pleases the listener.

Here is my view regardless of hybrid or all tube.

single gain stage: Pure, more open sound. Less dynamic, roll off top and bottom end.
multiple gain stage: wider bandwidth, dynamic. More complex.

A good design of multiple gain stage can improve on noise level and transparency. It can also sound very open.
However, it is hard to do it right.

As far as hybrid vs all tube goes, the Power supply section do influence sound but either way is fine.
Mixed gain stages can be tricky. It can be quiet and dynamic at same time. However, poor mix can sound thin.