As creators of the WordPress service Nelio A/B testing we get again and again the question of why we chose a service model instead of developing a standalone plugin.
We have now (partially) answered this question on this blog post:
Five reasons why WordPress services are better than commercial plugins
where we try to explain the benefits of the SaaS model from the customer’s point of view (and with emphasis on the WordPress ecosystem though what we say is generally applicable to other platforms).
We hope this helps people hesitating to take the service option do the maths with a different perspective!