Many bass players believe that tube amplifiers produce a "warmer" or more "natural" sound than solid state amps and that they have a greater level of perceived loudness for a given amount of amplifier power.
Many bass players believe that tube amplifiers produce a "warmer" or more "natural" sound than solid state amplifiers when lightly or moderately driven, and more pleasing distortion characteristics when overdriven. Some also believe that they have a greater level of perceived loudness for a given amount of amplifier power.