And between SlimDX and normal DirectX with C# what would you recommend?
DirectX is a set of native COM-like libraries, but most of them are not well-behaved COM and so cannot be used via COM interop in C#. Direct3D in particular, which is what you're really asking about.
In other words, there is no "normal DirectX" for C#, you only have options that are wrappers (XNA is a very high level wrapper around D3D, as was Microsoft's MDX which is now deprecated and their CodePack which is now effectively abandoned). Your only sane choices are SlimDX or SharpDX, both of which will work fine.