@Daniel

"My guess is that the removal of PowerPC support is unlikely to have played a major factor in the reduction of memory footprint"

It is 100% likely, in fact. Mach-O executables ( which is the format OSX uses ) are distributed as so-called FAT binaries. This means that the executable code for both Intel and PowerPC architectures is wrapped up inside the same file. Now given the fact that PPC code is RISC code, it is as verbose as Finnish ( and about as understandable, meh) - stripping it out will often give a more that 50% reduction in executable size.