They’re ‘free-form’ frameworks based on the Stacks plugin. So instead of giving you a designed theme to work with, they let you create your own look and feel and give you loads of stacks elements to create menus, slideshows, columns, panels, contact forms, lightboxes, grids, galleries etc.
Foundation has been around for longer but both have their admirers and both are excellent if you prefer to have more control over how your website looks - rather than using a pre-designed template.
Whether one is more suited to what you want to achieve rather than the other is probably down to personal preference. Best way is to check out the many videos which showcase Foundation and Foundry and see which ‘chimes’ with you.
The theme is free - you’ll need to purchase the stacks. Although you can probably get by with the starter pack to begin with, you’ll almost certainly be back for the add-on bundles.
Mr Workman makes excellent video tutorials on most if not all of his apps. IMO this enables a user to actually get more utility. Utility - usability = value to the user.
Glad to see you joining the Foundation family Ron! I hope that you enjoyed the video that I sent you today. Here is the Getting Started video series that you will want to watch.