A 6A3 will typically sound a little thin compared to a 300B, as will a 2A3. Or perhaps one might view it as a 300B sounding a little fat compared to a 6A3 or 2A3 depending upon your system and listening preference. That's just the normal difference in sound signatures. A 45 will usually go even more in the lean direction from a 2A3. This is the thing that gets people changing from one tube type to another and declaring the change life affirming.
I tend to like the 300Bs lower mid-upper bass weight myself. Not saying it is more real or more correct. It just works a little better for my taste and system setup.
