For many guys out there it's just a question of preference: many Eclipse developers hate to move to Visual Studio and many guys used to Visual Studio hate Eclipse. Apart from that, Visual Studio debugger seems to be a bit more intuitive than Eclipse CDT. E.g. adding a simple watch variable with Eclipse just takes twice the time needed in Visual Studio: an extra click here, an additional step there... If you are used to Eclipse, you are probably used to doing those things, but many guys out there moving from Visual Studio find those extra steps quite distracting and productivity-impeding.
And what's most important, the entire Android NDK bundle is normally tested on Linux and if you want to run it on Windows, you're pretty much guaranteed to see a couple of cryptic messages here and there caused by version incompatibilities, path glitches, etc. Our Visual Studio plugin contains workarounds for most of the known problems Windows developers encounter with Android NDK, so it saves major time setting up a new project.
There are many flame wars on the Internet on the "Eclipse vs Visual Studio" topic and I surely don't want to start another one here. Essentially, if you are happy and satisfied with Eclipse, there is probably no advantage for you to move over to Visual Studio, but for many guys, companies and game studios used to Windows development our plugin offers a major productivity enhancement when they are moving to Linux or Android.