Square grids can be as good has hexagonal ones if diagonal movement is allowed
That would actually be better, seeing as you now have 8 options of movement as opposed to 6, I suppose?
Yes, I actually believe it to be better. All that is needed to make it work is to have diagonal distances be multiplied by the square root of 2 (approximately 1.4). Obviously if the movement cost is counted by cell it is problematic, but with an AP system it's not an issue.
The Field of Glory creator (which is originaly a tabletop game) argues that human perception works better with 2 orthogonal dimensions than with hexagons (not his exact words but what I got from it).
A hexagonal grid is a 2D plane discretised along 3 axis, which is weird.
One big advantage of a square grid is for buildings. When you look at the upcoming Zodiac Legion, the square buildings clash with its hexagonal grid, and the hexagons actually have segments of different lenght (maybe to adapt to the square buildings ?) which skews the perception of distances.
Just to be clear, I am not arguing that hexagonal grids are bad -- I like Battle Brothers and hope Zodiac Legion will be good. But I am annoyed (triggered ?) when people say that hexagonal grids are always superior to square ones.