I voting for 1 bit 
Simple and Easy to remember and talk 

Agree.

Yes, this one makes more sense.

Your customers will have a far better idea than me or you. I'd suggest providing a mechanism for them to choose what they're comfortable with - just like eCommerce sites offering users a choice of currency - and use a sensible default (either BTC or - probably better for small amounts - Satoshi).

Whatever unit you decide to adopt, I recommend appending the price in bitcoins in paretheses, perhaps in grey text or a smaller font.  If you find this too cluttered you might consider a tool-tip.

For example:
    35 µBTC  (0.000 035 BTC)

Satoshi.. or maybe dust

calling 1bit is easy then other options

Is that a song?

I use:

1 BTC: one bitcoin
0.1 BTC: ten bitcents or zero point one bitcoins
0.01 BTC: one bitcent
0.001 BTC: one millibit
0.0001 BTC: ten thousand satoshis (edit: or one pip)
0.00001 BTC: one thousand satoshis
0.000001 BTC: one hundred satoshis, one microbit or one mike
0.0000001 BTC: ten satoshis
0.00000001 BTC: one satoshi (obviously)

So I voted for "100 satoshis".

Not many people agree with that.