Looking for some suggestions and guidance. Later this year my family of 5 will be using BA miles to fly one way from Hong Kong to Sydney.

Both Qantas and Cathay have mileage seats available.

We will be in economy. Looking for comments/ideas on which carrier will provide the most leg space, most comfort, best service, etc., since I've never flown either one.

Also, does anyone know if either of these carriers will allow upgrades when are tickets are BA mileage free?

Thanks!