When the goal is a lasting healthy running body, it's better to build this over a long and consistent period, mainly with flats in slow, easy training with enough rest, is my experience.
The contact and good grip of the feet with the floor is relevant to build a firm strength in the feet, legs and body in bones and muscles, which serves a healthy nerve system as well.
Starting with flats only, I had to adjust to no quick results, this was a conscious choice to serve the body. This after my experience with multiple injuries with foam shoes, due to get quick results.