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.
Definitely a smoother, warmer break up. Less headroom than the JJ 6V6, not as crystally clean. Having said that, that is exactly what I look for in a 6V6, so I love them.
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.
I have no experience with the JJs, but like others have, I've replaced an aging set of RCA gray plates with the New Sensor "Tung Sol" 6V6s and thought they sounded excellent and similar.
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.
The TS is much sweeter tone but much less durable in my amp.
The JJ is louder and clearer and more durable.
If my amp could take it, the TS would be used but I blew two of them.
I bought a batch of 3 used old stock (TS, GE and RCA) that sound like the TS RI but are durable and last in my amp.