No.6 does not go through Aberdeen, the journey is at least 45 mins.
No.6A, 6X and 260 go through the Aberdeen tunnel, the journey is about 30mins or less.
Apart from bus, u can take green minibus no.40 from 登龍街 [size=-2](TANG LUNG STREET) in Causeway Bay (Causeway Bay Exit B, then about 5 mins walk.), the journey is about 20 mins.
Bus from Kowloon only no.973 (citybus) but the journey time is at least 60 mins or more. (not recommended)