For most systems roughly at this point the performance investment starts to steeply increase. It is very map size dependant
Improved ist the sweet spot for me as I don´t want to tinker around with the setting before every scenario and it should cover a wide range of recent gen systems with a good performace base, +/- as one sees fit. With my new battleship I could go higher but high fps - especially fluid camera movement/panning - are priority for me.
So on smaller maps and/or with a powerful system one can go higher for sure, some max it out on bigger maps aswell as they might favor better terrain/tree draw distance but the fps impact can be tremendous. I´ve seen players being content with what appeared to be 15fps why others aim for the tripple/quadruple of this.
Eventually - as often - it comes down to personal preference.