Pigmen are easier to work with than endermen. Starting with gold you transmute down to get iron and up to diamond instead of transmuting up once for iron and transmuting up two more times to diamond. They are also easier to contain and mostly harmless during a grinder leak.
Those satanic smurf/carebear hybrids from the Twilight that drop gold and wheat might also work.
I have both... Enederman is a little faster in my experience
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