“Enterprise” is not a field. I take it to mean “working with traditional businesses.” That encompasses a huge number of business domains and technologies, you can’t really specialize in “enterprise” in a meaningful way. I call those “companies that make money already,” as opposed to startups. Some of them will also have ML/AI work (in fact lots of them).

ML/AI is either research and startup work or already included in “enterprise” applications. Amazon, Microsoft, Apple, Google, Adobe, etc. are both enterprise companies and doing a lot of work with ML/AI.

If blockchain ever turns out to have real business uses, not just enabling the crypto circus, it will become enterprise too. At this point it looks like a solution in search of a problem.

With Enterprise I mean B2B/Consulting.

My recommendation is to make a decision based on the topic that excites you. Even if you take a job in a candy shop and enjoy it, you may end up doing really well.

As for the high risk assumption, given that you are just finishing your studies, any of the domains you highlighted will be a low risk for you. The job market is hot, so worst case you will find a job in other company.

The fact you are on HN means that you already on the right path.

Machine learning if you intend to stick in the field more than 5 years, Blockchain if you want to take advantage of venture capital and then make your exit with a sizable chunk of change once they collapse.