Originally Posted by The Saint
That's not a particularly good analogy, lacross and hockey are differentiated by gameplay, milsim and skirmish are differentiated by complexity.
There is a lot more that separates milsim from skirmishing other than complexity. It has to do with longer waiting times for action - a willingness to wait and stalk for long periods of time, of mimicking real world operations and operators, employing their methods as close as one can, its about reduced ammo loadouts to real steel levels (sometimes), and its also about operating in a unit and taking and giving orders. There is a lot more to milsim than just the complexity of a game. I've seen plenty of complex skirmishes too (and hosted them as well) - complexity is not the sole domain of milsimers. Calling skirmishing simple by extention would be wrong.
What separates the two that makes lacross and hockey good examples is the nature of the primary gameplay - there are significant differences that make the sport appeal to either one person or another. And there are those who are happy with both. But you would not see one team playing lacross and the other hockey on the same field/ice rink.