To be honest, there are a couple other small advantages the iPad has over the Surface RT. I did not conduct any sort of scientific analysis, but the battery life of the iPad seems better. I didn't have any issue with the Surface RT battery, or getting through the day without recharging, but I did feel like it drained faster and required more charging in general.
The other plus in the iPad column is the display. This is another area where I don't have any significant complaint about the display on the Surface RT--it is bright and vibrant, and the text is relatively crisp thanks to Microsoft's use of ClearType technology. But, pixel for pixel it is simply no comparison to the Retina display of the iPad.
In the end, though, both are great tablets. The base Surface RT offers 32GB of storage capacity--twice that of the entry-level 16GB iPad--for the same $500. But, Microsoft has engineered the Surface RT to be paired with the Touch Cover, and the combo will set you back $600 (or $620 if you want a Touch Cover in a color other than black). Of course, as noted above, if you want the benefit of 4G wireless connectivity the iPad starts at $630.
Sign up for CIO Asia eNewsletters.