Using micro mscorlib, on iOS, what do you lose?

Very specifically, does anyone know some or any examples of, what you lose,

when you choose Stripping level of micro mscorlib. This on iOS. Thanks!

Is it a fact that, shipping iOS product made with Unity: "You should choose stripping micro mscrolib" - ?

To be sure to be sure: I assume that the stripping level has NO effect on PERFORMANCE (code execution speed). It affects only delivery size. I'm correct in this assumption?

Does mscorlib stand for MSFT Core Library ?

I already know what you lose by using .Net 2.0 Subset - nothing to speak of !

http://answers.unity3d.com/questions/266507/using-net-20-subset-what-do-you-lose.html

Thanks!