How many units will be alive at a time? Thousands? Millions? I can't see the memory used for a few stats in each unit being that big of a deal. And, putting those stats in each unit leaves you the opportunity to change them individually in the future. Lets say after 1 unit kills 5 enemy units he raises a level and gains 1 attack point. Or, if the player upgrade a facility in his game, then the ground forces created by that facility have a higher attack or defense...
In other words, I think leaving that stat as part of the unit doesn't use that much memory and leaves you the choice to change it in the future.
In other words, I think leaving that stat as part of the unit doesn't use that much memory and leaves you the choice to change it in the future.