In my experience, the problem with vendor: What if a feature is missing? I see this often when I am forced to use a vendor product. And, on day one, no one (hands on) usually knows anything about the vendor product, so there is a huge learning curve. If you follow NIH, then you organically build knowledge in the org. And features can be added with time+money. (Sure, some vendor products will add features, but usually for an insane price tag.) You cannot win either way: They hardest part is knowing which one to choose.