I am not sure what SPEC get upto, disregarding MacoSX for the moment, when you run Eclipse (Oil & Gas res management number crunching package) on a 1024 cluster of PPCs and then run the same thing on Pentium cluster - albeit under Linux with kernel extensions to handle the environment - the oposite is seen. I can probably get documented proof of the latter statement.
I found the same with SETI stuff as well, ok PC people pooh-pooh anything thats not MicroSoft or Intel not - so much the AMD lot, maybe its becasue they think for a living - I ran 100 cycles on a G3 450, it was weeks faster than the Pentium III running at nearly double the clock rate. Wheres the sense in that given the above remarks. I ran the G3 450 from home using a modem and ran the Gateway P111 933 at work on a high speed LAN.
I manager SUN, SGI, IBM, Linux, Mac machines mostly but also HP, Dec and VMS stuff so I am pretty cross platform as well, but I don't find the same results, I find it to be much more varied than that.
My guess is, what you really "understand" is nothing more than what you WANT to believe in.
Tiger Woods is not be the fastest player on the PGA, but he is the best.
I don't consider market penetration to be a good benchmark for how good a machine or operating system is, probably how cheap its is. The latter point is easy to illustrate, just open one.
I run quite a lot of different stuff at home, PCs (W2k and Linux of different flavours)), Sun kit and its no contest the machine I prefer using at the end of the day is always the Mac, by miles...........
For me Aqua ontop of UNIX is the a solid move, whatever hardware its eventually runs on, well for me anyway I work with UNIX for my living.