BF256B

That's as maybe. I preferred the BF244 with the "proper" pin out with centre gate. Both of those are made from unobtainium it seems, so would you rather have a BF256 or nothing?
Please support your statement about "subtle". What exaxctly does that mean? Transistors don't do subtle. The do have performance figures you might quote instead.
 
...the only differences which might be would be due to layout. If the 256 has a different W/L ratio to the 245/244 then I agree there would be a difference. But you could say "slightly higher gain" which explains things better than "subtle". However, in the IDss range this might not make a significant difference to actual performance.