I’m Nick, creator of Depth, and do want to point out some very big differences.
I’ve always been passionate about getting visual details right in webdesign, and have made fair amount of high priced client sites. For my own work, I came to loath using frameworks, and I have tried most them all, including Twitter’s Bootstrap, which is what Foundry is built on. IMO, frameworks are just that, a framework, but don’t yeild a finished custom feeling product without A LOT of work tweaking and adjusting said framework. I’ll pause, and clearly say I have little experience with Foundry itself, but I know it envolves mixing many stacks together and tweaking a lot of settings.
So how is Depth different? Prior to making Depth, I never used Stacks and RapidWeaver to make custom sites, I custom coded everything, it felt faster and unrestricted design wise, but then again - I’ve been doing webdesign aggressively for 10+ years. Long story short, I made a stack (Depth) that focused on making polished/finished looking site sections, that would have near every setting I would use for the design within that site section. I never set out to make a framework, but rather something that could make fantastic, complete, custom feel client sites - in a fraction of time.
Depth (for the most part) envolves you working with 1 type of stack, VS. Foundation and Foundry you working with many types of stacks.
Depth comes with over 750+ premade site sections I’ve made, that you can copy and paste in your project, swap the content and backgrounds and be done, and it will look and feel great on desktop and mobile. I’m not aware of anything close to that for RapidWeaver. Since making Depth, I currently am making 2 different client sites exclusively with Depth, and so far the clients are very very happy. I will certainly share these clients sites when they are done. Let me know if you have any questions.