When comparing X86 and ARM, remember all software for one would have to be re-compiled (with a compiler that supports ARM) to run on the other, even with the same OS. That would prevent anyone needing/wanting older non-open source software going to ARM. And would slow down adoption, thereby slowing down software going to ARM. It's about like going to Linux, except that it would have all the libraries etc. (kind of like Wine tries to provide) necessary. Of course, Linux is already available for ARM, complete with software.