The thing to be careful of with the HSBC card is that the rebates aren't guaranteed - they're not part of the core product (only the standard 0.4% is). Everything on top are based on promotions, such as an overseas spending promotion that just happens to have been extended for a few years running.
Also note the T&C - there are limits to the actual rebate amount:
Cardholders who have successfully completed the Registration and conducted Eligible Transaction(s) with an Eligible Credit Card for a cumulative Net Spending Amount (as defined in Clause 7 below) of HK$3,000 or above (the "Spending Requirement") in each Phase during the Promotional Period are entitled to receive:
i. an extra 5 times RewardCash (equivalent to 2% RewardCash rebate) on Eligible Transactions (the "2% RewardCash Offer"). In respect of the 2% RewardCash Offer, each Cardholder is entitled to receive a maximum of an extra $300 RewardCash rebate in each Phase. This is in addition to the basic RewardCash (i.e. $1 RewardCash for every HK$250 spent, which is equivalent to 0.4% RewardCash rebate), giving Cardholders up to 6 times RewardCash (equivalent to up to 2.4% RewardCash rebate).
ii. another extra 5 times RewardCash (equivalent to 2% RewardCash rebate) on Eligible Overseas Transactions (as defined in Clause 5 below) conducted with an Eligible HSBC Premier MasterCard® Credit Card (the "2% RewardCash Offer for Premier"). In respect of the 2% RewardCash Offer for Premier, each Cardholder is entitled to receive a maximum of an extra $300 RewardCash rebate in each Phase.
Correct me if i'm wrong, but (i.) refers to the base 2.4% reward (not the Signature/Premier bonus, or the 2% from selecting 'overseas spending' category). That means one must spend $3,000 each phase to be eligible, and even then only the first $15,000 of spending would apply (max. $300 RewardCash).
Since (ii.) doesn't mention Signature cards - and I couldn't find a clause that does - I assume there's no limit for the additional 1.2% those card holders get.
I also assume no limit for those who choose 'overseas spending' as the reward category (but i've put mine into supermarkets, so I don't get those anyways).