I haven’t directly compared the two, as I got the EL-34 a month ago and have left it in since, finding no reason to pull it and compare. Off the top of my head, I’d say the EL-34 is a bit clearer and more balanced, with a similar bit of warmth, perhaps a bit more. It also has the advantage of being shorter and not needing an anode wire, meaning less worry about vibrations affecting the cap connections over time.
I was maybe a bit too hard in my comments above about the RCA 5U4G I picked up. What stood out immediately in its effects were its bass, much more pronounced than the 5R4GY — I had turn down the subs a lot — and its richness is the best I’ve ever heard. It’s also got a great deal of delicacy. I do find its mid and highs and its lateral staging a bit constrained, and its perspective a little recessed. Some of this can be overcome in pairing, such as with the big stage and excellent presence of the Treasure Globe in the preamp. With that tube, it swings. Past that, however, I find its effects more attention getting than emotionally engaging, which is too bad. I wouldn’t be surprised if to another set of ears and system it would be just right, because it does have a lot going for it.