Hi there,
To me, the ED and ET are very similar e-body valves, with the only difference I can see is that the ET has a soft seat option as standard, but even then, the ED has up to class V as option.
Also, both the ES and EZ are unbalanced types, so quite similar.
I've looked around, and can't seem to see any guideline on why you would select an Ed over and Et, and the same, why an ES over an EZ.
Any input on why or a link to a document on why, would be great.
thanks
Gerard