They are similar, though there is a little difference. Could also just be that it is transconductance difference. The tennis balls test NOS, but not as high as the ST shape ones. The 101Ds are sort of like experiencing every detail of a piece of music. It's really like you hear every single part of the recording. It is still musical, but it is more clinical. I use this with Seas Exotics based speakers and it sounds great. The details are all there and you can hear absolutely everything top to bottom.
As to the 300b, they are more engaging and almost as detailed. The midrange just explodes from the speakers in a way I never anticipated. You just cannot stop listening. Yes, it may sacrifice a very little bass and detail, but you do not miss it because of how realistic the instrument reproduction is. It really is how it should be. Not sure how else to describe it. The acoustic guitar is just magic.
Now, are they worth the cost difference? Probably not, but man that is hard to call.
Shawn