I've owned most of the old reliables, Boss DD3, Ibanez EM5 echomachine, real vintage EP3 echoplex, out of all of them I enjoyed the real echoplex the most but it was noisey needed alot of maintenance. For a simple single pedal the EM5 gets close to an EP3 as well as the El capistan.
So.... all that being said for rack quality like delays with great algorithym models, ease of use, flexibility, stereo/mono routing, layered delays you cannot go wrong with the Boss DD500 version 2.0. I use the SDE3000 and echoplex EP3 models the most... both sound excellent.