I'd rather have two GTX 460's personally. They're a better, more refined product over all. And if you're comparing two GTX 460 1 GB cards versus the GTX 465's, it's probably a fairly close match anyhow. Two GTX 460 1GBs will outperform a GTX 480 as much as 20% in some cases. So it's a stellar performance setup.
Here are two separate reviews @ Guru3d.com that review the GTX 460 768MB SLI & GTX 465 SLI.
Performance between those is basically identical. Keep in mind the GTX 460 1 GB performs better than the 768 MB version due to having more processing units. The GTX 460 768MB does fall behind with Metro 2033, likely due to having less RAM. So I wouldn't put much value in that particular benchmark if you're considering the 1GB version (which you should).