If a SaaS solution solving your need, then generally we recommend going that route, why pay to build something custom when an existing product already does the job? However, often vended solutions don't get firms all the way to where they need to be.
We typically see this when a firm is looking to build something unique that allows them to have a strategic advantage over their competitors. In that case, we recommend building a product or a series of integrations from the ground up.