C# or Java ? Which language should i learn ?

Hi guys, i want to learn an oriented-object language and i don't know which i must choose : Java or C# ?

I know some basics rules about programming, i have made many cli-programs in C and some for my calculator in Ti-Basic.

I think with Java i can, at long term, develop on Android systems and i think it's the future platform of programming but...

With C# and .NET maybe i can make native software for Windows and Windows Phone, and the future marketplace on Windows can be good. But maybe the Windows/Xbox family is on decline and near to the end ?

So i don't know which choose, if you can give me some advices, it will be great. Thank you.

PS : Sorry for my bad english language. I hope you will understand what i want to say.

>>19
using mono.simd, it's not uncommon to get performance an order of magnitude better than .net

I'll give you that under certain conditions, .net is faster than mono on windows though.

Also which .net libraries is mono missing?