Maybe recently, with impulse responses and Fractal Axes-like machines, you can get any sound from silicon. But in the 90's the difference between silicon guitarrists (Dimebag Darrell or Chuck Schuldiner) and tubes was clearly noticeable.

Also, some 90's lower end amps with a valve in the prev sounded way better than similar priced amps that opted for pure solid state, at least for metal music and high distortion. For the clean channel the difference between them was minor.