My take?

The MS is a far superior version of the TA06 Pro, and Tamiya's answer to what people were doing to the TA06 in the last couple of years, since it's initial release. Two companies have come out with conversions for the TA06 since then - as R32Golf said.....Exotek and RSector. The MS is Tamiya's rendition of the Exotek conversion, since that came out first. The RSector is relatively new, and is different in many ways, not the least of which is it's rigidity. There is no way to adjust flex in the RSector, so suspension adjustments must be more precise.
The problem I see with the MS and Exotek, is the "swing away" electronics plate. I'm not a fan of swing away anything, and having any electronics that move is not a good idea. Which leaves the RSector as the only real alternative. The price of the RSector conversion is also a big selling point. If you are interested in the RSector, you can also get it straight from the manufacturer, which is based in Georgia, so you would get the conversion faster from them, rather than a vendor in California. The price is the same, so it would be up to you.

Even with the RSector conversion, though, you would still want some option parts, to improve the TA06's performance, whereas the MS is fairly complete, so there's that, too.