i did a backward calculation of buying a 1 whole lot in hkd of a few sdr n found that u are at a losing end upfront of >2%
yr commission plus clearing fees etc is not even 2%!!
Based on your calculation, is it cheaper to buy the parent or SDR? Thread title and what you wrote seems contradictory
Problem is SDR they take the trouble to set up they will try to make back through 2 things
1. Commission
2. Spread.
Should the SDR become illiquid and people not interested in buying and selling the spread depend on market maker who may cause spread to be wide.
If you buy direct you incur a exchange rate some brokerages charge a forex conversion of ard 0.8% ...
If you buy and sell often you should have a multi currency account so that you stick to using HK dollar and avoid exchanging to sgd.
If you just buy and hold for a few years both ways of investing will not make a big difference as the commissions and fees are amortized over long periods and would be negligible compared with capital gains/losses.
If short term trading, both are bad because commissions are high. One way would be to trade the ADRs listed on US instead and use a near zero commission broker like IBKR.