Hi Ben ,
Thanks for the nice words !
Now on your question - SIncerely, I have got no idea which one would be the better approach :) .
I guess it is a matter of UX decision . From a developer's point of view I would rather recommend the approach with RadDataForm in row details rather than as a popup .
1. It does not need additional button (edit) = less clicks for the end user.
2. It does not need special code to show / hide the form.
So, less code = less stuff to support = less things broken = less bugs .
Also it looks to me as a bit more MVVM - friendly.
the Telerik team