Not the op, but at some point I did choose between the two paths/jobs assuming I will get more proficient in only one of them each year (which is true, I stayed junior in C#).
Why I chose Java boils down to two reasons:
- runs on linux (I know there is some version of c# that eventually opened up, but I kind of expect it to have lot of conditions for being cross platform, I assume that standard c# code is not crossplatform due to some reason (e.g. Com usage might be standard way of doing stuff), which would make finding crossplatform answers tedious)
- whole ecosystem is more open source and more involved parties (which I interpreted as abit less controlled by the corporate overlord, so if corporate overlord went rogue, greater chance that language would survive somehow)
Never needed to call into C though..