The Samsung slate was 5.11 times as fast. Question: how much of that is down to the Core i5 being a faster CPU, and how much is down to a less well optimized Chakra engine?
Incidentally, the Apple iPad 2 which has an Apple A5 processors running at around 890 Mhz is approximately 33% slower on the SunSpider test. Since the CPU is clocked 45% slower that is a good result for the iPad 2 and Safari.
A Google Nexus 7 on the other hand which has the same Tegra 3 chipset as the Surface is about 55% slower than the Surface, which is poor.