That said, I agree Java seems more "pure". It's always seemed to me more like something a professor would have designed to show off OOP, while C# was more a marriage of that idea with all the convenient things programmers wanted but weren't quite as "pure". A more practical language.
The real downside of .net was always the way it was linked to the MS ecosystem. I don't think i'd trust Mono with anything mission critical to this day, so if you weren't in a MS shop that would be a strong disincentive to even consider it.