The discourse.org hosting is provided by the same team who develop discourse. Discourse Hosting is not affiliated with the core development team. It stands to reason that we (discourse.org) are much more familiar with the ins and outs of the product 
We also are the ones who drive the software,
based on feedback from our customers.
Our hosting is more expensive but last time I heard about their offering it was much less fault tolerant. None of our hosting plans are run from a single physical server: even the standard plan is spread out amongst many servers for extra reliability and performance.