@hifinubee I would look at your auditions reflecting the refinement of taste you've achieved by having experienced good components and sound in your own system.
You've likely found yourself in the unfortunate position of loving two components that do not mate well together. I won't tell you which direction you should go, but in most circumstances a 300B SET driving a B&W loudspeaker will not show either component at its best.
Again, I think because both the EL34 and 300B excel in the midrange some may want to draw comparisons even if hearing them side by side in two amplifiers implemented as similarly as they can come to allow an apples to apples comparison produces starkly different sound. One can always find exception with what I say going forward, but except in less typical situations, these descriptions should hold up... The EL34 has a tighter, more focused, more extended, and less romantic sound than the 300B. The EL34 produces low-frequency extension that easily walks away from the 300B. And of course, there comes the issue of output; one can obviously build a high-powered amplifier running EL34 far more easily than the 300B. The right EL34 in the right amplifier can produce a stunningly glorious midrange that reminds one of sunshine itself. The 300B often creates a lush and luxurious sound, again focused on the midrange where 85% of the music lies, that only a couple of tubes can compete with. The 300B can paint the sort of beautiful colors no EL34 can. Both tubes do well in the treble, but if one finds a situation where things get a bit too hot, it will be the EL34 rather than the 300B.
More than comparing the two tubes, I mentioned other factors contributing to how an amplifier sounds. It's taken me a long time to walk down this road. Conventional wisdom often holds transformers represent the most critical aspect of a tube amplifier. I used to follow that as so many have said it, but experience has taught me the effects of the rest of the amplifier, and I now consider that overstated. More than obviously, we overlook the differences in SET versus push-pull operation holding the highest position, even when the latter employs triode connection of the output tubes. After that, fixed bias versus cathode bias yield something akin to yin and yang, though it's the other way around. Some may not relate to this analogy, but think of how different a Marshall JTM50 amplifier sounds from the VOX AC30; they show the classic nature of each topology. After that come the others on my list, transformers, rectification, and the driver / phase splitter. Most know about tube versus solid state rectification, but even within that, directly versus indirectly heated tube rectifiers produce noticeable differences. On the driver / phase splitter stage less complexity produces the most direct and insightful sound and vice versa. That's another advantage of SET as it has NO phase splitter, and the driver circuitry tends to the simplistic
