Thanks to Vyacheslav Kalashnikov who kindly did all the work here so here are the translated 6E6P-E/6Э6П-E and 6Э6П-DR/ 6Э6П-ДР datasheets:
Looking at the 6Э6П-DR/ 6Э6П-ДР, there is a minor difference in the transconductance and anode current variance. Also the heating requirements are less demanding. Interesting to see though, is the fact that the 6Э6П-ДР grids can handle a bit more of extra power.
The proof is in the pudding, so we need to test the sound differences amongst these two valves and 6E5P/6Э5П!