I'm working on an app, its primary feature is rating/commenting on some kind of product (I used a banana as an example). I've got a problem with the tab navigation, please take a look:
In the first mockup we've got tabs (About, Comments, Related products) nested in a view, under the the basic information about the product. When the user scrolls down, the tabs will be fixed at the top.
On the second one, tabs are on the very top, which is absolutely more consistent with the material design and also will be more consistent with another app views (for example views with lists).
However, the first mockup has - in my opinion - better information architecture. Firstly we have the object name, then navigation (tabs) through this object elements: about, comments, related products.
I think that when tabs are above the product name, the navigation is too much separated from the product, but maybe I'm wrong, what do you think?