Dred's don't scream or moan, have their sight, and follow you until they find you, and have better names.
I'm assuming this is sarcasm. I chimed in on the discussion because the solution Oronk came up with to having both types are identical as far as I can tell with mine.
Which I thought 'cool'.
Terminology: As explored in various zombie sources, zombies will be called by various names by different groups, even within the same storyline.
'Zed' is a slang term from World War Z, but they used other names as well in that book. I went with 'Lurker' and 'Roamer' of the Walking Dead comics...but the group of main characters there ran into another group that called them all 'Biters'. So it's all a rose by any other name.
The zombies in my game did scream, in the Ragers mode (they were also called Infected from time to time, as well as Berzerkers).
The post-death version, the Lurkers, Shamblers, etc did moan. I never got into their senses too much, because that's all very biological and there was no one who was able to tell for sure. (I used Max Brooks' Solanum as detailed in WWZ and the Zombie Survival)
But I wanted them to 'somehow' be able to track by some unexplained instinct over days or weeks. This was a setting requirement because I wanted a major incentive for the players to either keep mobile or find a defensible place to hole up. Knowing that if you pass a couple roamers...you need to get enough distance before you camp for the night....or you'll have guests later that night.
(I have game synopses posted in that other link for those who want to see how it came into play.)