It's maybe an exaggeration to take the statement "there are no 64-bit PowerPC apps" and add all of those extra qualifiers to it. There may be a few, I don't know whether or not Aperture is a 64-bit app, and while LightRoom is a 64-bit app, I don't know if it can run in 64-bit on PPC. Beyond that, is Maya a 64-bit app on PowerPC? If Maya or anything else isn't, then there are no commercial 64-bit apps for PowerPC. Photoshop CS4 for Windows is 64-bit, and the first 64-bit version of Photoshop on the Mac, CS5, will not run on PowerPC processors at all, so unless you're writing your own code, or there's some other app I have never heard of, then I stand by the accuracy of my statement.

As far as the benchmarks go, they favor the Intel chips because the Intel chips are better, that's pretty much as simple as it is.

As the compilers go: Apple distributes the compilers for both PowerPC and Intel Macs, so if you think something is wrong with the PowerPC compilers, and it's very possible that different compilers could help the G5 out a bit, even though it's only really great at certain things, and even then only by the standards of 2003, then it would be a good idea to bring it up with Apple.