As you might have guessed, there's both advantages and disadvantages to using your own Name Servers vs. your hosting provider's vs. your Domain Registrar's (if the hosting provider & and the domain registrar are two separate entities).
In either of the three scenarios, yes, at the end of the day, it all boils down to the "company's resources" of whom you're using. But some companies are bigger than others and have more resources than others. At the same time, these bigger companies are more vulnerable (visible) to being attacked (DDoS attacks, for example).
There's also the chance that someone could fat-finger a configuration change for one of these large providers (think: Amazon's infamous April 2011 Outage or GoDaddy's recent DNS Outage.
At the end of the day, my opinion is that there's not much of a difference between the hosting provider vs. the domain registrar if they are separate entities UNLESS you are working with a small hosting provider that doesn't have the technical know how but think they do. (I emphasize this, because there's several smaller hosting providers that certainly DO know how to manage their DNS appropriately).
However, your hosting provider may have a number of features that integrate nicely into a "DNS Manager" which then easily integrates into their services as a hosting provider. I can't think of any good examples off the top of my head, but this would be 1 good reason why it might make sense to go with the hosting provider vs. the registrar.
That answers your question (I think), but here's a couple of related thoughts I have on the subject of hosting DNS (self-hosting vs. domain registrar vs. hosting provider):
I'm not saying that companies that self-host their DNS are vulnerable to the issues Godaddy experienced earlier this year as well. However, they are smaller targets, and let's face it: nobody values a company's website as much as you (the owner) do. You're going to pull out all the stops to get it back online.
My personal preference is to manage our own DNS servers, because we have the expertise to keep them operational, and we have worked to ensure redundancy, should 1 of the DNS servers fail. (But we're also a hosting provider too, so it only makes sense that we provide this offering).
Outside of this bias, I'm also of the opinion that companies that have the technical know-how should be willing to self-host their DNS for the reasons I've stated above. I'm a huge advocate for it, and at the end of the day, it puts the control of the domain into the hands of the owner, which is where it should be.