Yeah, I only briefly dabbled with Flow myself a few years back. By the time I got around to looking at TS and Flow again, it was clear TS had won.
Someone asked me the other day why TS had gotten more popular than Flow, and this was the summary I gave them:
> Early on, Flow was considered to be better at actual type-checking. But, the TS team has kept cranking out releases on a monthly basis, and mostly caught up in that regard.
> The TS community put a lot of effort into defining types for libraries, which convinced lib authors to write libs in TS, which convinced people to adopt TS because there were more libs with types.
> Meanwhile, the Flow team was pretty quiet, there were complaints about Flow sucking up memory and crashing, and Flow anecdotally seemed to have a lot of breaking changes in its analysis that made upgrading a pain. (The breaking changes were likely making the analysis better, but compilation errors are compilation errors).
> Eventually it hit a tipping point and TS adoption reached critical mass. Now, very few people outside of FB use Flow.
Reason looks interesting, and it's certainly got some very smart folks working on it, but it's still very much at the "niche experimental toy" level compared to TS.
