There's a way to reconcile both of you two's arguments. The continuity that exists within the Chinese government allows it to make longer term investments, ones that don't have to justify itself by the next quarterly report (I'm exaggerating, but you get the point). Having a stable, prosperous, and friendly Pakistan is in China's long term interest, so even if some of the projects don't offer good returns in and of themselves, it could still end up being profitable for China over the long run with improved export market, energy security, etc.
With that said, even many private firms in China are implicitly backed by the government, and the state banks can be nudged to give better access to credit to the private firms who intend to take on projects in CPEC. Most infrastructure projects, particularly in the transportation sector (roads, rails, etc.) are not profitable, but the economic benefits they bring to the regions they traverse can be invaluable as long as proper supporting infrastructure is built as well. This is why democracies and particularly private companies are ill suited for infrastructure projects. A lack of consistent, long term vision can render a large infrastructure uless, e.g. building a massive port but nothing around it to use it (see Hambantota) in a democracy. Inability to fully take advantage of the benefits the infrastructure brings, e.g. rise in real estate, retail, tax revenues etc., often dooms private firms.