The Peacekeeper benchmark has some glaring flaws in the benchmark code:

http://weblogs.mozillazine.org/bz/archives/020664.html

(For example, "The benchmark starts with an array of 100,000 elements and removes 20 elements for each call. After 5000 calls, the calls become no-ops, and the benchmark then times those no-ops.")

Gah, I was about to say that Opera beats Chrome at Sunspider on my machine, but then realized I was still running Chrome 5. Just upgraded. Here are the Sunspider numbers on my machine:

Chrome 5: 315

Opera 10.60: 287.2

Chrome 6: 279.2

Point taken.