Quad 3GHz Mac Pro vs Quad 2.5GHz PowerMac
Barefeats provides benchmarks comparing the Quad 3GHz Mac Pro (Xeon) vs the Quad G5 2.5GHz Power Mac (G5). This represents the new top of the line vs the old top of the line Mac.
They provide benchmarks for both non-Universal and Universal applications between the Mac Pro 3GHz, Mac Pro 2.66GHz and PowerMac G5 Quad 2.5GHz.
The top-end Mac Pro performed well compared to the Quad G5 with both Photoshop CS2 and After Effects 7.0 despite running under Rosetta emulation on the Mac Pro. Universal upgrades to these applications should provide additional performance boosts.
Meanwhile, Universal applications iMovie HD 6, Final Cut Pro 5, FileMaker Pro 8.5 and Cinebench 9.5 generally showed substantial improvements even in the 2.66GHz Mac Pro vs the 2.5GHz PowerMac.
There's no doubt that both versions of the Mac Pro are faster than the G5 Quad-Core running Universal Binary apps like iMovie, Final Cut Pro, etc. As you can see from the four UB tests we ran in this session, the Mac Pro 2.66GHz was as much as 62% faster than the Quad-Core G5/2.5GHz. The Mac Pro 3.0GHz was as much as 85% faster.
Update: AnandTech provides their review/benchmarks of the Mac Pro.