There are plenty of listeners with extensive experience with all of the low-powered triodes that love the 300b for its midrange beauty. I personally think it delivers a slightly bloated and mushy bass, a slightly rolled off top end and less dynamic contrast than the 2a3 (I own a parallel single-ended 2a3 amp). On the other hand, the 2a3 might be considered a bit lean compared to the 300b.
If one can deal with the extremely low output of the 45, I think that is a geat sounding tube—deep and tight bass, good extension on top, clear sound without being lean (I have a pushpull 45 amp.