I have used the original Tesla E34Ls for almost 20 years, and still have enough in reserve(not for sale, by the way) to last me for some time. I also have a good number of the later issued JJTeslas, and yes, I have compared the two, and also feel the originals trump the JJs in the areas of slightly greater clarity and top end detail and deeper, more controlled bass. I also have a dozen Siemens made AEG EL34s, which though nice sounding, don't quite give me the balance I like with my original Teslas. At about the time I purchased those Teslas, I tried Svetlanas, but have never listened to the more current Winged C Seds. I attributed the same characteristics to the Svetlanas as Ponnie has to the Seds---not involving enough and lacking top end extension. I have not tried the EH or any of the Mullard EL34s, and cannot use KT77s in my Air Tight amps. Of course, these are my impressions utilizing my componentry. As they say, YMMV.