Valve amps tend to give a rounded off sound, the treble is noticeably smoothed off. The bass generally is less tight (flabby) than a typical Class AB, that said vocals tend to be textured and little more realistic.Unfortunately I haven't had the chance to hear a hi-fi system with valves in the signal path. They're probably a bit too expensive for me. However, I would like to listen to one some day.
Having said that my system sounds utterly satisfactory to me when I listen to it. It's one of my favourite things in life. High quality music reproduction. There's nothing like it.......
As I've always said, there's no such thing as a perfect amp, hi-fi has always been will continue to be a compromise.