[bodeadly]

Async is superior. I have done processes with locks in shared memory. I have done threads. But I predict Async will slowly start to take over. Processes are not suitable for working on shared data. Threads frequently yield race conditions and deadlocks even for experienced coders. But Async doesn't have any of these issues. So why isn't it more popular? For two reasons:

1) it completely breaks the functional programming model that we all learned as toddlers (instead of call A and then, after that's done, call B, Async is call A which just installs B as a callback, returns immediately and then an "event loop" calls B). Note that promises and tasks and futures are just "syntactic sugar". Personally I'm not a fan. I don't use any of that. I just use callbacks.

2) Even though Async it's great for concurrency, it's not great for parallelism. Everything runs with one thread. So if you want parallel processing you need workers.

But I would argue that issue 1 can be overcome. In fact, I find Async to be quite elegant. I think in the long term people are going to realize that maybe we've had it backwards all along.

Issue 2 is actually not that big of a deal for most things. It's actually somewhat unusual that you need to have some CPU intensive operation running in the background. Maybe image processing, data modelling, etc. But most blocking operations are just I/O operations which are not using CPU that much. If I needed to write some kind of network server, I would look at using libuv as a portable runtime.