Buying on IBRK vs Hashkey

I have bought & sold BTC on IBRK a few times. But now I want to buy back in & hold long term for retirement. I do like keeping all my investments in one place & don't need to worry about keys, cold wallets getting lost on IBRK.

SO what are the pros for buying on a dedicated crypto platform like Hashkey here in Hong Kong. IBRK HK is selling BTC in collab with OSL.
There are also BTC ATMs around but i believe they have large fees.