My vote is to NOT change BTC, but get used to talking in micro-BTC (UBT,UBC,uDTC,whatever the concensus), but that's not clearly available in the vote!
"micro" sounds too tiny when spoken aloud. I suggest a new name altogether. And it needs to be 2 syllables.
UBC is ok. But when spoken aloud, it should sound like "you-coins" (not "micro-bit-coins").
mBC is ok. But when spoken aloud, it should sound like "em-coins" (not "micro-bit-coins").
I wonder if mBC might be confused with "million". The m comes from micro, but obviously the real abbreviation for micro looks more like u.
So, let's go with UBC, pronounced "you-coins".
I'll send an "you-cent" to anyone who agrees with me
I suspect that people will just say "milli" or "micro", just like we now say "cent" rather than "percent of a dollar".
And mBTC will never be confused for MBTC. The context will always make it clear.