I owned the 6L6, but got caught up in all the hype about EL34s, so I sold it and got one of those. The 6L6 was just better overall. I was never able to recover from selling that one to get another 6L6, so I really miss the first one I had. Yes, indeed it's great with EL34's. The blue channel is a little bit better with EL34's. However, the clean and red channels are better with 6L6's. Essentially, for a slightly better blue channel, get EL34. For better clean and red channels + an arguably as good blue channel, go with 6L6's.
The low end high end are better with 6L6's in my opinion. The crunch on the distortion is also better with 6L6. If you have to have EL34s, go with the 101B. If you want the 20th, get 6L6. Some people will swear on EL34's, but I really think that's mostly just an EL34 preference. The 20th is actually a bit better with 6L6. The clean channel just isn't the same with EL34s. The red channel sounds kind of like the Ecstasy Red pedal with EL34s. There is also a difference in the touch sensitivity which is better with 6L6. However, having said all this, if I had either, I'd keep it and never sell it again.