Almost 200k invested in local brokerages. Thinking of switching to Interactive Brokers (IBKR). Should I?

By local brokerages, I assume you mean DBS/UOB/OCBC.

If you have overseas investments (not on SGX), you're paying a custodian fee per ticker you own.

Assuming you don't invest anymore, you still need to pay this custodian fee for as long as you own shares with these brokerages.

By switching over to IBKR, you won't have to pay a single cent in custodian fees, though you will incur either transfer fees or selling/repurchasing fees.

I don't know how many more years you intend to hold your investments or how many tickers you have, so you need to do your own calculations by comparing the recurring costs of the custodian fees vs the one-time cost of the transfer/commission fees.

And if you do plan to continue investing, you should do so with IBKR regardless of the above decision because IBKR definitely has better fees + FX rates. The only exception to this is if you're investing in SGX tickers and want them in your CDP account.

Diversification of plateform risk. One plateform down in one day, still got spare