The only reason I say easier is because c# is easier, more user friendly to code in. I lacks the requirements to knwo pointers and memory allocation, which is complicated. LUA and Angelscript use them. That in itself makes LUA and or Angelscript to create from scratch.
Sorry, but that is just wrong. Lua has garbage collection, and I can't remember ever juggling pointers when coding. Angelscript I don't remember too well, but last time I checked it was garbage collected at least. C# was never intended to be a scripting language, being much more like Java in its overall architecture. So it will offer you few of the advantages of explicit scripting languages.
I think you are not fully aware of the advantages of true scripting languages.
That is one of my concerns. From a programming point of view, C is hardest then C++ and C# is easier. Significantly. So given LUA is similar to C and Angelscript is similar to C++, the from an ease of use, C# is easier.
Being based on C has no actual influence on the language. I'm not sure what you actually mean with that - lua is not in any way like C. Its table system is very different from C. If anything, it's a bit more like Modula. And yes, it is implemented in C, but so is Python. I'm sure no one would accuse Python of being too much like C.
And if you know a scripting language, c# would be easy to learn, not so the other way around.
So from an ease of creating a mod, c# would probably be the best overall.
For whom? The people creating mods will, in all likeliness, be the fans of your game. They will not be programmers. For them, understanding the concept of programming is already hard enough. If you know no programming at all, or only very basic concepts, learning a scripting language that is friendly to non-programmers will be easier than learning how to use a more complex language that has very little tools to facilitate scripting and modding.