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?