I don't think there's much competition between x86 and s390. You'll use the later only if you're already an IBM mainframe customer and don't plan to migrate off.
For Power vs x86 it probably matters a lot what type and scale of operations you're at. As far as I can tell x86 typically has the better price/performance ratio but then I think there are quite a few supercomputers that use Power so there must be some advantages (probably mostly I/O related).
For Power vs x86 it probably matters a lot what type and scale of operations you're at. As far as I can tell x86 typically has the better price/performance ratio but then I think there are quite a few supercomputers that use Power so there must be some advantages (probably mostly I/O related).