That isn't a "normative" statement about better, but a "positive" statement about a trade-off of expressive power versus rigor. A bit of mathematical intuition suggests that formally asynchronous approaches tend to be less powerful and hence more rigorous. But if your spec is still in the prototype phase, taking on a lot of expressiveness and permission with respect to your domain model is desirable because it gets you an end-to-end solution sooner.

What is good is not "on time" or "robust", but "on time and robust". Necessary and sufficients.