The future of RIM is likely QNX so I`m not sure that I would say MS is on a better path.
The kernel-level choice of OS platform really doesn't matter much at this point, as all the players have "modern OS kernel" features in their platforms.
What really matters is the framework that provides app developers with an environment that increases their productivity and tries to enforce consistency between applications. This is where WP7 is much better than Android, for instance.
RIMs primary app strategy seems to be emulating Android apps, with a secondary strategy that is basically copying the webOS framework (RIMs version is called WebWorks). They also offer Adobe Air as another development platform, but its hard to say how seriously developers will take that option. I'm not sure what RIM wants you to write a 3D game in for their Tablet OS.
It goes without saying that applications that come from those three frameworks will behave very differently from each other. Just like how Java client applications are 2nd class citizens everywhere they go when compared to native apps on a OS, Android applications will be numerous but will seem awkward and "different" from the the apps that are developed using WebWorks which will be different and the apps that are developed using Adobe AIR.
By contrast, Microsoft has a much better strategy, and a much clearer message for developers: use Silverlight for building WP7 apps unless you're building a game, in which case use XNA. Having two different dev environments in the WP7 case makes sense because the needs of an app with buttons, lists and fields is much different than one that is building Halo for your phone. The three application development frameworks that are offered by RIM you can build an app with buttons, lists and fields, and they will have a different look and feel.
Finally, RIM hasn't even started migrating it's Smartphone user base to it's Blackberry Tablet OS yet. Which makes me wonder what they will call it when they put it on Smartphones. The Blackberry Smartphone OS?