What Does a guitar Processor do ?

Basically, it emulates what the individual pedals do, distortion, chorus, delay, reverb, etc. To me the processors just don't come close to sounding as good as individual pedals. So for instance you can buy a Boss ME-25 multi-effects processor for $199 and it does a bunch of different effects. You can buy a Boss DD-7 pedal that only does delay for $179. So you really can't expect the processor to be of the same sound quality as the individual pedal. Of course there are much more expensive processors that would sound better. To me it's just a compromise. You give up sound for convenience.