I don't think this article was one of the better articles in 3dworld... Every software has it's strenght... the renderer in Maya was allways a "little" problem -)
If mr for maya stays free than there's not even one thought to change to something else!!
Look what XSI costs. In version 2 you didn't even have particle in the cheapes version. I think that changed in version 3... but anyway, the price was high before AW changed the price and the price for XSI is still really high.
I don't think that the particles in XSI are really useable. I worked with an XSI artist to export particle simulation from Maya to XSI through the dotXSI converter. If Maya will support particle in MR than you don't even need to use the way over XSI.
Volumetric shading was allways an problem, or better they didn't implement anything that you can call that way. It's getting better in the default renderer and will hopefully end up with an MR shader that works...
Another thing is the stability of XSI. I know only one company here that uses XSI and they're integrating Maya right now... and what I heard from them, they complain a lot about XSI.
Another thing is the API. In Maya you can make hardly everything with the API, if you understand how it works. The XSI API, what I've heared from an programmer, is much easier to programm. But it's by far not that flexible and in-depth...
I don't think that you can compare XSI subD with Maya's and every bigger studio with Renderman can tell you a story about subDs and so-called-subDs...
Anyway, if it makes sense to use XSI, why not, if you can afford it. For an Maya artist it's pretty easy to change. I like Maya...