The main difference is that Halifax was a small backyard operation with a few outposts. It had a single director.
Interactive Brokers is a very large corporate entity that is listed on the NYSE.
Apples and oranges.
That said, any and every broker is potentially susceptible to fraud or compliance breaches. We only need to look back at MF Global a few years ago.
As usual, the safest course of action is to diversify. I have my SMSF, which trades the Growth Portfolio, housed at Macquarie and is protected with the HIN based system. I’m actually looking at Open Markets as a new provider. They’re 0.07% rather than the Macquarie 0.12% and have the same HIN protection.
PS; I dealt with the Halifax owner many years ago when I was launching managed accounts. I ran for the door after we spoke – he was clearly dodgy.