Best Practice for loading data into data model

mmcanelly Roche's Maxim would dictate:

1. SQL Server
2. Power Query
3. DAX

That would be "best practice". That said, best practices are merely guidelines, there is generally a lot of nuance to them, like you favoring ease of reverting changes for example. I would say that if you run into issues with refreshes taking a long time then you might have to implement the DAX solution instead but otherwise, PQ is probably the say to go. It is kind of annoying how PQ handles this sort of thing though in terms of not seeming to cache the query load but doing it all over again each time. Referencing Power Query queries - Power BI | Microsoft Learn

That said, if you switch your Fact table load to a Dataflow, then you could potentially speed things up as the article above indicates.