Bare Feats has some interesting benchmarks of the new Mac Pros. (Could they have labelled their charts any more confusingly? I doubt it.) It’s also nice to see they’re using Geekbench instead of the lamentable Xbench, although Geekbench doesn’t try to do the many things that Xbench does so badly.
As I expected, the new “base” 4-core Mac Pro is slower than the old base 8-core Mac Pro, so that for the $200 you save over the old machine’s price you lose significant CPU performance, albeit not as much as you might think (it looks like ~10%)! The new CPUs have double the memory bandwidth of the old, and with their considerably superior graphics cards in the end are probably better balanced machines. Oh, but the memory requirements are annoying (you need to buy your RAM in sets of three for optimal performance with one 4-core CPU, and six for two 4-core CPUs).
I’m using a (borrowed) 2008 8-core Mac Pro and it very seldom makes use of its extra cores. So I guess the new machine looks like it’s probably slightly better value, all-told, than the model it replaces. Nothing like the value proposition of the new Mac Minis though.