You seem to be under the impression that SE Linux is a Linux distribution. It isn't; ***it's a set of standards for one***. I'm unsure as to how you can state that it is exactly the same thing as SXE ("SXE is SELinux rebadged") given that you then go on to say that you don't know what the differences between the two are...

Anyway, SEL (I think like AppArmor) is about providing native Unix processes with security protocols. This has very little to do with the SXE approach, which is about implementing a safe virtual machine (which makes more sense in a heterogeneous hardware environment because if it is implemented correctly, as for some versions of Smalltalk and Lisp rather than Java, gets you cross platform capability without re-compilation.)

Unlike SEL, SXE *is* a specific implementation - which includes, but isn't limited to, a Linux OS.

So in summary, SXE and SEL are about as unlike as two computer security initiatives can be. Standard vs implementation; native code vs virtual machine.