How safe is it to have your etf / shares in a custodian account (IB, Saxo) vs. CDP (DBS Vickers, UOB KH)?

If it is for long term and you have these feelings then I would just pay the fees and store it in a CDP.

I personally don't worry about it because in the bank end they are all interlinked - IB uses state street for example and so do a lot of asset managers and even banks so if state street went down, everything is doomed!

Also an informative article by Seedly - https://blog.seedly.sg/cdp-vs-custodian-account/

If these big financial institutions go bust at the same time, it means that the world world is going through a financial meltdown, worldwide crisis etc, other investors' monies would not be spared as well. So you are not the only in a "sinking ship", why worry by then.