In the CS community, it's well known that BSD is more stable, secure, and the best OS for critical infrastructure, while Linux is more friendly, flexible, and better for hobbyists or businesses that can save money (by hiring cheaper Linux fanboi rather than expensive real computer scientists).
Actually, in my experience in the CS community I'd say that it has gone more and more Windows centric. There are good points (Windows Server is obviously a lot better than XP these days) and not so good points (et al etc etc
) to that, but it seems to be the trend regardless sadly. I'm seeing more and more "critical infrastructure" running on Windows as time goes on, even more so as people rush to outsource services (no matter how critical) to "the cloud" and similar hypervised systems. I suspect that this says more about corporate sponsorship than actual technical benefits.
If I was setting up an online exchange, I would use Red Hat Linux for the public-facing front-ends.
I would use Red Hat Linux for the database servers, both master and slaves.
But for the critical stuff, such as the bitcoind instance, email, and SSL, etc. there is no choice except for the decision between FreeBSD and OpenBSD. I'd go with OpenBSD for the firewall, and FreeBSD for bitcoind. NetBSD for email. My users would get nothing less than the most secure set-up available outside NSA.
I wouldn't. I wouldn't do any of that. Far from it, the first and only thing I'd do is outsource all the technical requirements to a third-party company. Probably one such as the one you own/work for. Then I'd put in place a whole load of over the top SLAs so that when (not "if") the brown stuff hits the fan, I can pass all the blame on to you.
The biggest danger in the world of the internet is not whether one uses Windows or Linux or OS X or FreeBSD. The biggest danger are one-man armies who think that they can knock things like this together all by themselves. No matter how clever you are, or how much experience or qualifications you have, you still need to eat, sleep and visit the toilet.
The reason that we get so many up-start disasters like this is precisely because they are set up by people who think that they are going to do one better than the last person. And there is always someone waiting to come along who will think of something you didn't think of. You can have the best operating system in the world, but if Doris the cleaner unplugs the box to put the vacuum cleaner on, it all goes down. Taking responsibility for other people's money is a dangerous game wrought with risk, and I wouldn't touch it to begin with.