AIX is just another flavor of *nix. If you know HP-UX or Solaris you can pick it up. There are some differences in commands and what not. Speaking as a Bell head that also worked on MVS I can see where the MVS people influenced AIX. Many of the AIX subsystems are very MVS like which is not necessarily a bad thing.
Personally I like C/C++ over Java. Have never cared for Java. To me the language has always appeared bloated and unreadable object.object.object.function = object.object

. It made me insane and I stayed away from it. In my experience its not as quick as C though they say it is now. C if written properly is insanely fast.
I do neither now. I dabbled with Objective C for a while before 5 billion people poured into the Mac environment for the new gold rush with mobile apps.