IMHO, one of the great disadvantages of a PEQ is that once it is tuned to the masters ears it may sound odd to others. For instance, my 60 year old ears are less sensitive to the 4K-6K band so I may actually boost those frequencies to a point where it sounds weird to my wife who, as all wives do, has catlike hearing. The room corrections which use a microphone to set the processors DSP are at least trying to make the system neutral so that it sound natural to most people. I think that for the most part, higher end equipment tends to shy away from manually adjusted PEQ to discourage users from making their equipment sound different than intended.