I guess both are better in terms of configuration. No much difference but both are better than Unity framework. Why the hell you need marshalbyrefobject association in dependency control. But if we compare spring.net and Castle Windsor both are good. But question comes which one is complete container framework.
Like we need Aspects for validation on Dependency. So winsor utility fail. I guess it’s stupid to compare String.net with Castle Windsor or anything like such because all are utilities and spring is complete container framework. And all folks who say it’s heavy please check memory leak issues with all. It’s not spring or Castle Windsor , it’s stupid way of writing code.
So finally answer is if you need just DI use Windsor but if you need complete framework for any solution use spring.net.