Tab groups have been replaced with layout groups from 7.3.1, which offer better performance and flexibility. Tab groups are based on the Yahoo User Interface (YUI) library, which is no longer supported on the Pega 7 Platform.

User interface rule forms now use layout groups instead of tab groups to place layouts in forms.

Layout group is responsive and Tab is not. It's a good UI practice to design the screens so they render nicely on different form factors. Layout group used as Tab would allow you to do that. If you use 'Tabbed layout', the screens may be desktop friendly but on phones the screen will have horizontal scrollbars which results in bad user experience.

Please find the pros and cons of the Tab layout :

1. 'Refresh when active' - You may set any tab to refresh when it becomes active only in Tabbed layout
2. Default active tab - You may set any tab (not just first) as default active tab
3. Tab position - Tab position may be changed from top to bottom, left or right

Cons of tabbed layout -

1. Styling is a painful process
2. Not mobile/touch friendly
3. No enhancement planned for future

The Layout groups are the alternate of the Tab groups.