Well, I can give you a reductionist, and highly subjective rigmarole based on limited experience with products sporting 300b, 211, 845, 2a3.
All tubes can be usefully operated in a no-feedback circuit. Good stability. So, basically they're VERY good amplification devices (i.e. better on paper than the best transistors for example) despite the need for output trannies. Having said this, more or less, objective piece -- here goes:
300B, good because of availability, reasonably priced tube and trannies, the worst of the lot in extension and sonics. Excellent tube for marketers, but other tubes are catching up. Reasonable linearity and some dynamics. Low power -- but still workable, somewhat (say a 112 db spl 1W/1m speaker). Basically this is a "nearly" tube: it's nearly good, nearly extended, nearly excellent sounding, nearly...
As such it lends itself to many applications -- for this very reason. I hate this tube in any application EXCEPT for powering an upper midrange driver alone. Maybe a tweet, but wouldn't know where to buy suitable output trannies.
2a3: as above for availability etc; good pricing to boot. Much better sonic attributes than the 300b even, BUT minimal power capabilities. Probably has excellent dynamics, bass trable, mid, lush and clear, veil-lifting and all that -- but given most speakrs' abysmal efficiency, you'd need an army of 2a3 to hear them. In which case of course you'd lose some of its quality attributes. Life's tough.
845: not too good availability (but improving), expensive, and variable quality trannies all expensive. Good power and extended linear region. So, so, low freq. (so what -use a mosfet instead). I like this tube -- but it's depressingly expensive in most implementations.
211: now we're getting serious. Availability starting to get better and you no longer have to be Mr Gates or similar to obtain it (but being rich remains an important consideration). Trannies still awfully expensive. High voltages. Now this is where SET leaves the whispers and enters the premier league. Good sonics, good extension and no bulls...t driving capabilities. In fact, it also has reasonably low output impedance to boot!
1610: one you didn't mention. Very serious driving capabilities, better stability with loads than 211 and capable of excellent energy swings within linear operation. BUT, very limited availability.
_______Voila___
Let me repeat that I'm personally comparing these tubes to one another -- so when I say I hate X tube it's an exaggeration and said in context -- right?
And if s/one offers me a 300B, I'll jump on it!
Cheers
