My opinion is that 30 mA thru a 6V6 tube is going to sound like 30 mA thru a 6V6 tube. The difference between tubes seems like a better explanation. I would not think that the 14 W tube would need more current to sound like the 12 W tube. It means that the 14 W tube may be able to take 35 mA and the 12 W tube may not take it as well. Just my opinion EDIT: I take it back. Rebasing from 70% of 12 W MPD to 70% of 14 W MPD would be an improvement in tone.