There's a whole lot more to it than valves vs. silicon. There's a reason an ACC stack sounds like it does, solid state or not. Output transformer capacity and other circuits matter a lot. Some tube amps sound great. Some sound awful. I have heard Ampeg amps that sounded sickly medium to light brown. That's not what a bass should sound like, even if you don't follow the colors. It had tubes, but it may as well have been a Lucas amp. It sucked. I have heard other valve amps, 7ender often enough, and a massive Plush (!) that sounded great. I'm personally not big on dirt with the bass, and I'll leave that to an overdrive pedal or fuzz pedal so I can make it go away.
For the purposes of a touch of overdrive, I currently have an EXH Bass Soul Food on the board. That's the one non-utility pedal that's there for now. It's not the kind of soft clipping that you get when a tube amp starts to distort, but it's always there if you want it, meaning I don't have to kill the back of the room to get it.
We can get into wave forms and all that if we want, but there's a whole lot more to it than just valves vs. silicon. There's cabinet design (check with Mark on that one), and you name it.