The test measures touch latency, or the time between a tap and opening an app, using a special bit of hardware. While the latency is generally small — less than one or two tenths of a second — you can see a big difference between products in this output graph.
Why are the Apple devices more responsive? My guess is that Apple has the most integrated approach when it comes to hardware and software. Android device makers might have hardware expertise but they’re still working with Google’s Android software. Here’s a technical explanation of how graphics work on Android, which offers a glimpse at why touch is implemented differently in Android than it is in iOS.
Nvidia may have an edge over others here — showing lower relative latency — because it developed Direct Touch tech that offloads touch processing to a CPU core and boosts response times. Although most people don’t think of Microsoft as a hardware company, it did design the Surface products and therefore has direct control over the hardware and software integration for touch on the products.
At the end of the day, how much does this matter? To most people, probably not much. I have a new Nexus 7 tablet and although the TouchMarks data suggests double the touch latency of an iPad, I don’t notice or see any touch lag.