its the same but XBT is easier to type than micro, and like i said we need ISO name anyway that's why some of us are trying to convince people to start using something simple for all to make adoption of bitcoin easier. Also when you are using 50 µBTC or 50 mBTC there is still chance to make mistake because its only one letter difference.
mBTC and µBTC are being used in standard Bitcoin-QT client, so I think it must be more convenient for most people.
Then maybe you can explain me what for we have 3 options now BTC, mBTC and µBTC if we could have just one ISO XBT like USD EUR PLN GBP and other currencies.
There is no reason to complicate things for newcomers and make things not consistent for everybody.
I know people think its not important but when you think about it, then you will come to the conclusion that it is.