I replaced the JJ 6V6's in my Morgan Deluxe Reverb clone with Tung Sols and thought they were much smoother and less harsh. A nice change IMO. THEN I got a matched pair of NOS Raytheon 6v6GT's and the Tung Sols will serve as back ups.
I bought both the JJ's and Tungsol RI's. I don't exactly know how accurately they were selected for my amp, as no set worked acceptably on the intended bias setting. However, with a EL34 bias setting, the Tungsol's stayed in, the JJ's are in 'storage'.
It's really amp dependent. Supposedly the JJ's which I like are more like a 6L6 not a true 6V6. The JJ's can take a lot more voltage. It might be best to find out what voltage the amp operates at and go from there.
I found the Tung Sols to have break up earlier than the JJ's.
It will depend on amp voltage as to what you have to use. I have used the Tungsol RI 6V6's in a 5E3(cathode AB1), and a Gibson GA-8(series class A). Fat, harmonic, and loud enough. The voltages in a DR (class AB) are very high. YMMV.
I like them in my (modded) 5E3 build. Lively, balanced, nice high-end sparkle. Definitely an improvement over the EH which were a little dark, though not as warm as the Mazdas that were there previously.
I liked the JJs in that amp as well but I haven't solved the rattle problem with those. Haven't given up on them yet.