32-bit vs 64-bit Vista Benchmarks
The folks over at 64-bit-computers.com have published an article comparing the performance of 32-bit and 64-bit Windows Vista, and they’re using Geekbench as their benchmarking tool.
From the article:
Both 32-bit and 64-bit tests were done on a budget AMD Sempron 2800+ powered desktop PC, featuring Asus K8U-X motherboard with 512MB of main memory.
The 32-bit Windows Vista Ultimate achived 99.8 GeekBench points, while the 64-bit version of the same OS gained 110.7 points.
(via Digg)

It may be usefull to weight the tests a bit better. Almost all of the 10% performance difference came from only one test – Dot Product. The rest of the tests, except for Jpeg decomp, and some stdlib are about the same between the platforms.
I am not sure what kind of average you use for the Geekbench, but in this case it’s missleading.
64-bit not recommended… yet
Theoretically, 64-bit systems should be faster and more secure. However, it currently boils down to lack of support. In most cases, the lack of support far outweights any security benefits.
You’d almost expect to see 2X the performance still, yet in many cases it’s within just a few percent. In a few years, once 64-bit software truly reigns we’ll see the entire computer optimized for 64-bit and we’ll truly see some gains. By then, Solid State Drives should be operating at 100MB/s or higher so we’ll see some impressive benchmarks indeed.
*A very important thing to note is that some versions of Microsoft Vista are shipped with both the 32-bit and 64-bit versions in the same package. Apparently, if you get the 32-bit you can also get the 64-bit for a nominal fee if it’s not included. Ask around first and don’t be surprised if most people don’t know what you are talking about.
So, if you are switching to Vista you’ll likely wish to go 32-bit until 2008 or 2009 then likely backup your files and do a fresh install unless you can update from 32-bit to 64-bit by then.
64-bit is definitely coming, but it’s not quite ready.