I think the main difference is the additional modes for example with the Trinity and this there are different reverbs not available in the hall of fame as well as having similar modes. Same with the PGS delay it has the echorec sound that is different. I dont expect people to buy all three just choose the one with the sounds they like the most. As far as changed reverbs I like the Digitech Supernatural the most think PGS came up with some awesome sounds for that. Thinking of getting a Flashback X4 though!