> With Flow you don't even have to opt-in to a new syntax. You can just use comments:

So you use a opt-in comment-based syntax instead of a opt-in non-comment based one for type-annotations.

Hardly a big difference.

> Using really powerful inference you can also write much fewer types

I'm just going to assume you didn't know typescript does this too.

Typescript is nice. You should give it a try once. You may end up surprised:)