I want to make my own game but I'm undecided which should I use which would be better as I have knowledge in c# & c++ but not in xna & sdl ? thank you
If you have knowledge in both, you should be able to make your own mind up to what you prefer using. XNA is just Microsoft's game framework for the .NET framework. It can be used in C++ as well, though if you're using Visual Studio you are limited out of the box to C# or VB. It also depends what kind of game you want to make, if you are targeting Xbox homebrew or Windows Phone as well as PC, XNA is probably the way. SDL has the advantage of being portable to Android, Linux and Mac. So you choose.
hmm I haven't exprimed myself correctly , I'll edit original post too I have knowledge in c# & c++ but not in xna or sdl which one would be easier to learn as I'd like to make a pc game ?