First of all, let me tell you that you can now write apps for .NET with Python. There's a python implementation for the .NET framework called Ironpython (in beta 5 now).
Regarding XML, I can't tell you much but in general, python is much easier, cleaner, concise and intuitive than all the other alternatives you mention. Being a dynamic language, you can achieve more with less lines of code. Easy tasks are easier with python, and complex tasks can look simple with too. I also think that Python is an excellent first language to learn. Learn it, get used to think as a programmer, learn the basics (functions classes, oop.) and then, when you're reasonably comfortable, you'll be ready to pick any other language (or you'll be happy enough to know that you don't need to learn any other one). -- http://mail.python.org/mailman/listinfo/python-list
