both are for c, but there is a good wrapper for gtk (gtkmm).
gtk has its own look, so theres no skinning of ui elements on the user side(with windows styles). but i like to programm with it more.
win32, mfc, .net are mostly limited to ms visual studio, while gtk is very hard to use with vs.
you should have a look on win32, .net, gtkmm and qt. just try to write and compile a simple hello world program with them
upsides of win32:
downsides:
- no classes, only c with handles (very crappy)
- in my opinion very bad documented
upsides of gtk(mm):
- easy to learn/programm
- good documented
downsides:
- somehow difficult to install the development files
- no native windows look
