Desmume is great it has Wifi support and doesn't crash on HG/SS. It runs very slow but it has a gba slot and you can change the size of the window. Nocash needs a program called nocash zommer for that
NO$GBA to the win!
DeSmuMe is too slow and loses some parts in some sprites...
NO$GBA has its own 3D renderer which makes it go 1.5x faster than OpenGL.
Also with some great options in NO$GBA 2.5c