Sometimes this is true, sometimes it's not, and I can't make heads or tails out of it, either way. I have a passive switch on my CB six string and on my Stambaugh fretless. Depending on what effects are on, sometimes passive really makes it sound clearer, other times, it makes it disappear, completely.The double win is passive works much better with pedals as well.
My Wal is active, all the way, and that's fine with me, because it sounds so f***ing awesome, every time. It has an xlr out, and when I record, sometimes I just plug straight in the console. Engineers love it.