Gantry Framework provides backend management and a template.
We've combined Gantry Framework, removed the template, and replaced it with Bootstrap (as you download it from github). In our implementation, Bootstrap is a drop-in replacement. No compilation or customization is required.
Checking Gantry's default template, you can find the traditional classes for scaffolding like: rt-container, rt-grid-4 rt-alpha, rt-block, module-surround, module-title, etc. In the other hand, a pure Bootstrap scaffolding has a fixed or fluid grid system with classes like: container, row(-fluid), span(n), etc.
Gantry's default template has Bootstrap flavour (some common less files). It's an evolution on the previous templates.
We are developing new apps based on Joomla & Bootstrap, so we prefer a pure Bootstrap / Gantry framework implementation.
Regards,
Anibal