I've been using new-production WE 300Bs in my Kaiju for about a year and a half. I think they sound great, but the only other 300Bs I've tried are the stock EH and Gold Lion Genalex. The Genalexes sounded a bit better than the EHs but it wasn't a dramatic upgrade. The WEs, on the other hand, were clearly an upgrade, noticeable from the first seconds of firing them up and listening to them: clearer, smoother, and more vivid-sounding (something like the sonic equivalent of color saturation in photography/cinematography).
Is the improvement commensurate with the price difference? The WEs cost roughly 5 times more than the Genalexes. Honestly, they don't sound 5 times better, but what with "diminishing returns" and all that, I'm not sorry I spent the money.
Were I wealthy, I'd try Elrog, EML, and Takatsuki 300Bs as well. Maybe some day.