Recently-ex-sell-side here: retail investors generally don't need to worry about this at all. There's a lot of protection. Your assets are held separately from the firm's assets, you have SIPC insurance, and there are enormous amounts of regulation in place to try to prevent you from even needing to rely on those two mechanics. Really the worst that could happen is it might be a headache to get to your stuff for a small period of time while something is figured out as to where your assets are going if your brokerage just up and poofs.

That aside, I generally trust the discount brokerages a bit more than people like BofA/Merril and Wells Fargo and JP Morgan, just because I feel like the discount brokerages are a bit more content to just sit on deposits and earn interest (interest accounted for > 50% of schwab's revenue last year) rather than get up to highly leveraged hi-jinks or open fraudulent advisor accounts.

IB for sure, it’s not even a question.

Any chance you can explain some of the reasoning, even if it's a bit esoteric? One thing that's keeping me from going 100% IB is the lack of a transparently-stated fraud guarantee, like Schwab/Fidelity have. Other than that, IB seems like the best.