How about not using them at all? I prefer BTC and I hate that I need to calculate back and forth between different denominations.
yes i prefer to call that 10k satoshi , 100k satoshi than uBTC and mBTC
For real transactions of goods and service (from a cup of coffee to a Lamborghini), I think it is okay to stick with "BTC".
For microtransactions (eg. faucets), I think it is better to use "satoshi" instead of 6 zeros after the decimal point IMO.