Re: Pro Co Rat 2 or Marshall Guvnor 2
I've owned both of those pedals and, while I like both, the Rat 2 is the one that I would consider more unique and more interesting. The Guv'2 is good at giving you a pretty wide range of Marshall-flavor distortions, but there are a lot of pedals that will do that. The Rat 2 gives you that extra something -- character, I'd say.
If you have an amp that doesn't give you any distortions that you like, and if you happen to like Marshall-type tones, get the Guv'nor 2. That's a serviceable range of dirt that you can dial in, and it may well help you decide what you want for your next amp. If you want a great pedal with a voice of its own that you'll be able to pair up with different types of amps over many years -- probably getting something different out of it each time -- then get the Rat 2.