Hey, just had a look at their mod. I think the approach of this mod is different in that it develops existing units to stay relevant throughout the game by giving them evolutions into new units and changing the rewards units receive at different ranks (new ranks now yet added).

It also adds some new units, but these are meant to fit into the cultures' playstyles and strengths. For example with barbarians, the sunderhoof is essentially an upgraded sunderer. It fills the same role of harassment and flanking, just better. The Vandal can function like a weaker, more mobile berserker. Finally, the Chaos Sewer, while filling the role of a batllemage that barbarians didn't have before, still fits into the same aggressive playstyle.

With expanded units, it seems to focus on expanding the roster. It adds a lot of units that fill roles that were lacking but that other factions had. For example, it adds an archer unit to mystic. This mod won't add an archer unit to mystic as I view their cultural approach to ranged combat to be all about magic. Why use archers when they are already deadly at range via magic? (because you get a ranged physical dmg unit that performs well against foes with high resistance, which is functional, but not immersive and takes away cultures' weaknesses)

I really don't know that much about the other mod though or his vision for it.