I think tube amps and ss amps tend generally to have different bass quality. If you did a frequency response check, I doubt that a steady state frequency response check would show much difference.
But dynamically, there is a tremendous difference in each type's typical damping factor. Tubes are rather low and ss is rather high. A low damping factor can make the bass sound quite ripe and thus give the impression of a fuller bass. An ultra high damping factor can yield a very tight bass, which ironically can sound somewhat lean. But it really isn't. Synergy with the right speakers is key.
But dynamically, there is a tremendous difference in each type's typical damping factor. Tubes are rather low and ss is rather high. A low damping factor can make the bass sound quite ripe and thus give the impression of a fuller bass. An ultra high damping factor can yield a very tight bass, which ironically can sound somewhat lean. But it really isn't. Synergy with the right speakers is key.