Meh, the arguments for and against #pragma once are all kinda moot. The argument against #pragma once is that it's non standard, which is entirely true, but it's still quite portable. The argument for #pragma once is that it's faster, which is kinda false, since common compilers have optimized inclusion guards to effectively have all the speed benefits of #pragma once. My opinion on #pragma once vs inclusion guards: bleh.
This^^ there's no real difference. Just pick one or the other and be consistent.
Well one other argument in favor of #pragma once is that you can't accidentally give two header files the same header guard identifier. More the one person posting here has run into the problem of copying and pasting a header guard without remembering to adjust them for the new file.
This was the only thing that made me choose #pragma once... I've made that mistake before ;)
Currently the PS3 compiler doesn't support #pragma directives so you still have to be aware of both and for multi-console dev only use header guards.
Our PS3 compilers do (including the non-GCC ones)! We use #pragma once in the whole code base (as well as other pragmas too, like optimize off so that you can debug certain sections of code in 'release' builds), which compiles on quite a few consoles. Are you sure you aren't just using certain command line options that are requesting it to be 100% standards compliant?