There have been and are inherent flaws in devices and topologies that render the very best
solid A, AB amps sounding different than the very best vacuum tube components.
One of the largest differences are the large ufd electrolytic capacitors in the output stage of the amplifier.
This is due to the comparative low voltage/high current vs the high voltage/low current of tube
output stages. These large capacitors have high DA (dielectric absorption) and ESR (equivalent series
resistance).
Distortion spectra, odd number harmonics vs even harmonics, although HD and IMD can be minimized
with enough global negative feedback. But then some feel GNF has problems as well.
Some solid state devices can have high internal capacitances, high Miller capacitance, high DA of
insulating materials, high ESR of the materials used. Hexfets have been known
to have junction capacitances of .001uf, the junction capacitance varying with voltage applied,
up to ~25 volts.
Other SS devices have quite low capacitances, but still high DA and ESR.
An interesting problem I accidentally encountered decades ago involved bleedthru with reversed biased
1N914, 1N4148 diodes.
Too late to think about more differences.
cheers
steve