Following the benchmark of 3D capabilities test where the iPhone 3GS is “close to four times faster than the 3G”; in JavaScript performance, the new iPhone 3GS also blows away its predecessors as well as rivals, even approaching MacBook speed!

Medialets ran the SunSpider test suite with Safari 4.0.1 on a 2.0 GHz Intel Core 2 Duo White MacBook (as a baseline for relative comparisons), Mobile Safari on the iPhone 3G with iPhone OS v2.2.1, Mobile Safari on the iPhone 3G with iPhone OS v3.0, Mobile Safari on the iPhone 3GS with iPhone OS v3.0, the “Browser” app on the T-Mobile G1 with Android OS v1.5 (Cupcake) and the “Web” app on the Palm Pre with Web OS v1.0.2

The results of the iPhone-based tests alone are rather astonishing and seem to indicate that many of Apple’s claims about the performance gains of their 3.0 OS and the iPhone 3GS may hold some water. Using OS 3.0 on the same iPhone 3G yields nearly 3X the JavaScript performance in Mobile Safari vs. using iPhone OS 2.2.1. The iPhone 3GS ups the ante by another factor of 3, bringing JavaScript performance on the iPhone 3GS to just 12X that of a full-powered desktop machine that has well over four times the raw processing muscle alone. The T-Mobile G1 running the “Cupcake” version of the Android OS completed the test suite in about 91 seconds. This makes it about a third faster than the iPhone 3G running Apple’s previous OS (2.2.1). The Palm Pre came storming out of the gate with speeds that closely rival the iPhone 3G running Apple’s latest iPhone OS.

For full details of the benchmark test, see Medialets’ summary of results.