armored core has been through a number of changes in terms of gameplay and because of that it has a very split up community. some want to see it go back to its roots(PS1/2 era), others want to see it return to AC4/FA style, and others don't really care
to be more specific, its gameplay has a very weight-y feel to it and its more MP focused than any game in the series. theres also no choices or routes in story mode which sucks.
personally VD is one of my favorites. I also think its one of the better MP games out there.