Bootstrap provides a UI design decision "out of the box". If you don't have a designer, want to BOOTSTRAP your project, you will want to use bootstrap. It's great.
Foundation to me is more of a base css framework. You don't have (m)any visual styles out of the box (though it does contain certain styles) which is great when you need to create HTML/CSS to match a concept provided to you.
I love foundation and bootstrap, but to me they both offer two very different things.