A good, independent dev is possibly safer than any other dev. They can go where the market goes and live off the strength of their products. They won't ever find themselves beholden to a platform holder who's box is impacted by a novel input method, for example (think Rare having to make Kinect games whether they want to or not).
I'm not sure I particularly agree with this at all.
As if a developer is particularly worth their chops then whether they are first party or independent is irrelevent, as they'll continue to secure business and publishing for the games they make.
It's when a dev, like Insomniac or Rare for example, starts showing a lack of creativity and putting out a string of games that review medium to poorly that is the issue. First party devs imho are more secure in this case because a platform holder will "usually" be beholden to putting them to work on other, wider, platform strategy-driving projects, e.g. Rare making Kinect games, before looking at shutting them down. Whereas an indie in such a position has no recourse because it will be next to impossible for them to secure a solid publishing deal for their next project, see devs like GRIN, Factor 5 and a whole swathe of studios killed off in the previous gen.
I don't think that being bought out by a publisher makes a developers future entirely secure, as that depends wholly on the performance of the games they make (in most cases). But I would argue that it does offer a measure of greater security than remaining indie, because when times get rough then, after alot of your senior talents leaves, you have far less in the way of safety nets to keep you affloat.
Good devs that are first party, like Naughty Dog, Turn 10, SSM, PD etc will get a lot of freedom and resource to do ambitious projects too. And none will be in fear of being shut down in the near to medium turn, so long as they continue performing well and putting out solid games.
Devs like Zipper interactive and Psygnosis as you said had 6-8 years of funding for them to prove their worth and continue to raise the bar. That's far far longer than any external publisher will continue to fund the games of any independant developer that isn't putting out hits.
