This is a good discussion and I think you both make a number of important points.  Particularly, I agree that a for-profit model reduces (or can even eliminate) dependency on donors and therefore is both more sustainable and potentially more responsive to the needs of its constituency over the interests of its funders.   Also, Jose's comments remind me that there must be a large group of people who are socially-minded but not non-profit oriented, who are more interested in creating a people-positive enterprise than becoming fund-raisers or being beholden to donors.   Hybrid social enterprise potentially brings these peoples' energies and capital into play.

I think the for-profit social enterprise has a lot going for it.   For one thing, it has a self-sustaining dynamic, whereas a program based on grants is essentially on life support.  A for-profit enterprise also has a natural tendency to find opportunities to replicate itself, rather than being limited by available funding.

But what does it take to make a for-profit that's actually for-people?   Even if ownership is in the hands of a non-profit, that doesn't guarantee that the for-profit is itself a for-people social enterprise.   The non-profit parent could easily see the "greater good" of generating income for itself as trumping the necessity for people-positive behavior from its subsidiary.  For example, the Hughes Medical Group's ownership the defense contractor Hughes Aircraft in the '70's and '80's.  

I do think there's an inherent tension between profit-making goals and service-oriented (or altruistic) goals.  Regardless of charter, there are going to be decisions about allocation and focus of resources, pricing for goods  and services, and ultimately generation and application of capital for expansion vs spending on services or wages for which there are no right or wrong answers and on which right-minded people might easily disagree.   Particularly, a traditional non-profit mindset might lead to very different answers than a for-profit one.   The hybrid enterprise requires an alternative sort of thinking.  

One model that occurs to me is a for-profit that is designed to create an ecosystem of surrounding micro-enterprises for which it creates a market by purchasing goods and services.   This enterprise could be paired with a non-profit which provides things like micro-finance access and job-skills and training for the local entrepreneurs.    The central for-profit would have written into its charter a set of ethical guidelines, such as fair-trade and living wage practices, and a set of operational directives such as prioritizing local suppliers and graduates of the non-profit's training programs, but would be unburdened from directly providing services, and would be free to use its profits either for expansion or to fund the associated non-profit as it saw fit.   Whether this enterprise becomes exploitative is dependent on its management and ownership, and it might be vulnerable to being viewed in various lights by people of differing perspective, but I think inherently the model has some merit.

One might even take your question one step further:   are there particular types of enterprise which can only be successful when done as a for-profit?  And further, are there types of business in which for-profit social enterprises might have an edge over traditional for-profit businesses?