MCE? You mean the old economy
? (sorry for my ignorance if there's actually more to MCE than seat width that I'm not aware of)
It's really subtle. I'm surprised you can add an extra seat by just taking away just a bit of width from 9 seats.....means you have to remove 4 inches from each aisle as well. I guess with that many seats to take width from you can add a seat.
Hopefully if I ever plan on an ULH flight, I'll save enough for MCE, if it's definitely worth it?