We have both. Both sound great, and can be dialled in pretty similar really.
Funny but EL34's in the TJ didn't sound very good to me, it felt a bit thin anaemic all round, and we went back to KT88's. It really seems like that amp was designed around the KT's (transformers, depth circuit, power amp voltages?) so I would say don't go chasing unless you can't help yourself.
I also wouldn't get hung up how 'radically' different each brand of preamp tube are purported to sound by some. After extensive testing we've confirmed what I think many already know deep down - there's not much tonal difference at all. There's some variation in gain as expected, but comments like 'a blanket was lifted off' and 'it's impossible to get good tone with JJ's' is utter nonsense, unless you have a faulty tube. I guess these days the best tubes are the ones you can find.
Rehashed internet myths and forum hyperbole have gotten so out of control that you really can only believe 1% of what you hear. Including this? Maybe - try for yourself by recording close-miked clips and blindly comparing them later, preferably re-amping so the playing is identical. The blind part is critical, otherwise you'll hear what you want to hear!
Enjoy the amp and please report back