What is the preferred method and what is the difference between using const and import?
In 2016 it makes sense to stick with the import since that’s the part of the standard.
There is no technical reason to prefer import over require though: everything that can be done using require can be done with import and vice versa. In some cases one will be more concise, in another – the other.
To summarise: choose the one that fits the project code conventions/consistency.