I see what you are saying, and I, not having programmed the game, have no idea how the engine does what it does, but I can tell you what I am seeing. I would think that the battle map deals with a completely different set of problems, for which they have had several game releases to iron out, optimize, and improve. AFAIK, it’s unit rendering and the calculation of physics. There are obstacles, but no movement range, no zone of control, and no boundaries to figure out (e.g. coastlines). It could be a matter of optimization (or lack thereof) on the campaign map as you suggest, but I think the new design plays a part.

On the campaign map (and I was talking about unit selection lag, not the panning over the map lag), just selecting a stack of units gives you a lag, when all the program has to do is calculate and display the unit's range. Why? Probably because it also has to factor in 'no-go' zones like the coastline and enemy unit's zone of control in multiple locations within the unit's range.

Plus the lag is not uniform. I seem to get much more selection lag with multiple range unit stacks and in 'busy' areas than with one ship in the middle of the Atlantic. It has to be the interaction of the movement/zone of control range of various units, along with a ton of other constraints, that is causing this particular problem.

I think it is all more complicated that it would appear. Just look at the edges of your ship's movement range. You will see no evidence of any regular pattern, so the program has to figure it all out to he nth degree and then 'draw' that range or area of movement Add in a couple of coastlines and other ships and it all just takes time- or CTD. If the map was based on nice, regular hexagons, we would not have half as many problems.