We ran an unscientific browser comparison at work using a Galaxy Nexus, Z10, and an iPhone 5. Consistent results in terms of browser speed were:
Nexus w/ Chrome > Z10 > IP5 > Nexus w/ default browser. BB10 has a great browser but the Nexus with Chrome usually beat it by a hair, the iPhone 5 was surprisingly slower than both, and the Nexus with the default browser was the slowest. The Z10 had the highest HTML 5 scores. For BB to have a better browser than iOS at this point is something they deserve a lot credit for.