I saw Heart just after the Wilson sisters broke up with the Fisher brothers, and Steve changed basses after almost every song, and I don't think he did more than two songs with any bass. Honestly, I thought it was distracting. Levels and tones were uneven for the first few seconds after every change, and some didn't sound so hot.
My experience was the exact opposite--I saw Heart way back when (must have been mid-late 70's) and to this day I remember it was one of the best live bass sounds I'd ever heard at a big arena concert. Maybe 'cause I was sitting dead center, straight back near the board--who knows. I went to pretty much every big rock show that came through our area, and his sound really made an impression(and I wasn't even a big fan of the band yet). I just remember it being so clear and defined. If memory serves he played a P with a pick the whole time, and I recall it having that flatwound thunk.