With the upcoming ANT IPO, I would like to open a position in ALIBABA with the expectation that there might be a boost in its share price. Should I buy shares of BABA on the NYSE or 9988 on the HKEX?

Generally, there are no huge differences between the two stock in these two markets. They will both mimic each other whereby if the one on NYSE is up, so will the one in HKEX. This is also called a 'fully fungible' stock whereby you can convert your US shares to the HKD shares if you like.

Though some have mentioned it would be better to purchase it on the HK market due to the US-China relations.

Maybe you could look into which would cost more in terms of buying fees/transaction costs etc.