Another argument in favor: don't stick unnecessary levels of separation between you and the company that controls your domain. Only the very largest web hosts are also domain registrars, the rest are simply reselling another company's services. If there are problems, you're stuck dealing with them through a middle-man.
The only advantage to buying both hosting and domain registration from the same company is billing convenience, while there are numerous advantages to not doing so. Just choose an accredited registrar.
Fortunately, most accredited registrars that offer reseller programs allow domain registrants to claim back their domains and manage them directly through the registrars. So there's no stuck-with-a-middle-man issue as you described.
IMO the real danger is when the hosting provider is a registrar. Domain registrars have a lot of power, because for most TLDs the registry never touches your personal information - the registrars do. The registrars set the EPP code, which is the key to transfer your domain away. A reseller generally cannot prevent a domain to be transferred away if the registrant insists to (the most a reseller can do is to keep sending locking domain API calls).
The only advantage to buying both hosting and domain registration from the same company is billing convenience, while there are numerous advantages to not doing so. Just choose an accredited registrar.