If you don't need x86 compatibility, PPC is fine, and for open source stuff it's probably reasonably well supported in major distros.
But pretending you can have anywhere close to reasonable performance of x86 binaries on even the newest PPC chips is hopeful at best and realistically a fanciful notion.
When you run an application on QEMU on Linux, only the application code is simulated (by just-in-time compiling every basic block when it is first executed, then always just executing that compiled native code). System calls go to the Linux kernel on the host system, which runs as usual. Hardware is not virtualized. In contrast, Virtual PC (if I understand correctly) simulates the hardware of an entire PC, including graphics hardware, and runs all of Windows on top of that. That's a lot more expensive in terms of processing power.
That said, sure, you will probably lose some performance with QEMU. If the simulated code uses lots of fancy vector instructions that are not provided by the host hardware, you'll even lose a lot.
That having been said, I need to look into QEMU.
It's not like there are no options at all.