In your case, then yes you just want the card that maxes your mileage. Since you are looking to mostly redeem on long haul, you will find that Asia Miles will go further than Avios. Avios is better value than Asia Miles for shorter flights.

Have a look at the credit card thread to see which one will max your miles - you will likely find that Standard Chartered Asia Miles master card will be the most straightforward and earns a decent rate of miles. However, you might find that being new in HK, it will take you a few months before a bank will approve your credit card. They usually want to see a few months of salary deposit before they approve a card.