Clickability, a proprietary SaaS platform for content management, has compared SaaS to Open Source. Not only is the comparison inaccurate, it omits the downsides of SaaS and frankly, they are comparing apples to oranges. Open Source is a licensing and development model, SaaS is a software delivery model. Either they are distorting things on purpose, or they don't understand Open Source at all. In other words, time to look at some good ol' FUD and to share my take on Open Source versus SaaS.
To give you a sample of their comparison, take Clickability's take on integration:
One of the biggest advantages of using Open Source software is that there are no limits on what services you are "allowed" to integrate it with. Given the number of sites that Drupal powers and the size and strength of the Drupal project, official integrations with other software and service vendors are abundant for Drupal. If you need integration, for example, with a highly specialized, niche product or web service, it may already exist among the 6,000 contributed modules for Drupal. If it doesn't, you are free to create it yourself. The same is true for other Open Source projects. Good luck getting that into the development cycle of a proprietary SaaS platform.
In many ways, Open Source is actually less risky than putting all your eggs in a single proprietary-software-basket. If you are unhappy with a particular Open Source company or service, you can take all the code and go to the next company.
Or take their section on hosting and performance:
I won't even begin to debunk what they write on self-hosting — it doesn't have anything to do with being Open Source. Suffice to say that the great thing about FUD is that it validates our work in the Open Source community. They wouldn't have such a comparison page if they weren't worried about Open Source disrupting or slowing down their business.
My take on Open Source versus SaaS?
It is true that SaaS enables organizations to save money on hardware, configuration efforts and avoid hosting and maintenance hassles. However, proprietary SaaS vendors like Clickability need to ask themselves what happens when we start building SaaS solutions based on Open Source values. Open Source SaaS offerings, like Acquia's Drupal Gardens offer the convenience and support of SaaS multiplied by the benefits of Open Source.
— Dries Buytaert