No, neither one. But, the 6 Pro has an all tube driver stage, as well as preamp, and you can control the voltage to the driver tubes, and get a nice growly tube tone. I chose the 6 over the 4 for the eq section, 4 Pro is a 9 band graphic, 6 Pro has a 4 band semi parametric, like a Mesa. I like that. Also, 4 Pro can biamp, 6 Pro is single channel mono output. The difference in power is 100 watts, in favor of the 4 Pro. No big deal.