ARMv5 is a slow CPU for developing emulators of modern machines like PlayStation or Nintendo64.I'm curious about this, could you give more details?
PlayStation and Nintendo64 both use MIPS processors so are much faster to emulate on a MIPS machine because there is little binary translation overhead.
ARMv5 is generally implemented with a low number of pipelines and lacking some of the attributes required to keep them full, optimal MIPS code can be faster for certain things, and GCC is better at optimizing MIPS than ARM from what I hear because it's a more classic style processor. Also MIPS has double the number of useable registers and a few more weird instructions.
Having said all that, ARM is easier on assembler programmers and provides a number of features that can be useful in optimizing code a lot. Inline shifts, conditionals and fast block copy are just a few of the good functions. As far as software graphics is concerned I'm pretty sure I could optimize my algorithms far better for ARM than is possible on MIPS, also since most emulators rely more on graphics throughput than CPU emulation speed, I'd suggest that ARM would be faster for the more modern emulators so long as there is no graphical acceleration available.