I am aware there are other NAnt and MSBuild related questions on Stack Overflow, but I could not find a direct comparison between the two and so here is the question.
When should one choose NAnt over MSBuild? Which one is better for what? Is NAnt more suitable for home/open source projects and MSBuild for work projects? What is the experience with any of the two?
One of the major draws of MSBuild for me (on Windows platforms) is that it comes as part of .NET itself. That means that any Windows machine that is up-to-date with Windows Update will have MSBuild available. Add to this the fact that C# compiler is also part of .NET itself and you have a platform that can build projects on clean machines. No need to install Visual Studio behemoth. NAnt, on the other hand, has to be explicitly installed before a build can be triggered.
Just for the record, I've used NMake, Make, Ant, Rake, NAnt and MSBuild on non-trivial builds in the past (in that order). My favourite is MSBuild, hands down (and I do not favour it because "that's what Visual Studio uses"). IMHO, it is a very under-appreciated build tool.
I would compare NAnt vs. MSBuild to the difference between procedural and functional programming. NAnt is quite straightforward and you-get-what-you-see. MSBuild on the other hand requires a bit more thought. The learning curve is steeper. But once you "get it", you can do some amazing things with it.
So I would recommend looking at MSBuild if you also gravitate towards functional or logical style programming - if you are willing to invest a bit of time and effort before seeing tangible results (of course, I also strongly believe that the investment eventually pays off and you can do more powerful things more efficiently).