Maytag RR
My vote goes to the Maytag Reverse Rack machines that were made from 1970 until the late 80s. After they went to the reversing pump belt drive design in about 1974 they were basically the same machine all the way until the end of production (early models had a direct drive recirculating pump with a separate drain pump). They had phenomenal loading capacity and cleaned very well. The down side was that they were noisy when they were washing and they sounded like a freight train while draining! But then again, the 5 fills, wash/rinses and drains of the regular cycle only lasted about 35 minutes.
My favorite model simply because it was the dishwasher of my childhood was the WU601.
I have one of those awaiting a full refurbishment in my basement....