I have no experience with VN, but for AY vs CX I would most probably go for AY because the seat is quite nice and service is good, too.
If you have OW Emerald status, then however I would maybe consider CX because the F lounge at HKG is so much nicer than any lounge at HEL.
Here is a nice picture of the AY cabin:
http://www.finnair.fi//filecontent/c...0_business.htm