In Executor I get a Speedometer 4.02 CPU score of 40 point something on a 2GHz P4, 24.95 on my 1GHz Athlon.
A 1GHz G4 scores around 35 in native PPC mode IIRC (lower in 68K mode of course).
This is a 68LC040 emulator only so it won't do OSX apps. They are supposed to be releasing a PPC emulating version this summer..... unless it goes the way of SoftMac. The PPC emulating version of SoftMac was demoed/benchmarked on Pentium IIIs back when those were good, but has been delayed repeatedly, with the current excuse being that it is pending a lawsuit by Apple.
Then there is Basilisk II the open source 68040 emulator, about 1/3 the speed of Executor, but good enough compatibility I can play copy protected mac games CDs on it. There may be a PPC emulating version of Basilisk soon...