Backdrop CMS is our go-to platform for clients with complex Drupal 7 sites who want a stable, supported codebase for sustainable development.
As we mentioned, Backdrop is a fork of Drupal 7. That means that the Backdrop core team started making their improvements right on the Drupal 7 codebase, and are committed to being free and Open Source.
One huge benefit to this approach is that we can upgrade your site to Backdrop CMS. We need to run some updates on your modules and themes to make sure they're compatible with the changes Backdrop has made, but the work is a drop in the pond compared to the work it takes to rebuild a site from scratch in either Modern Drupal or WordPress.
In fact, an upgrade to Backdrop costs roughly one-third of what it takes our team to rebuild from scratch, and that's not the only highlight:
A move to Backdrop means a move to a platform that centers organizations where resources aren't unlimited. The Backdrop Core Team is committed to sustainability. This means a focus on backwards compatibility, and a mindful approach to significant changes. (Check out their Philosophy page to hear this in their own words.)