User Centered Design and Material Design Guidelines both helped on tablets and phones, but they did not help the same layouts equally.
Two teams can both say they improved a website, and both be right, while producing very different results. The difference usually comes from the process they followed rather than from the changes they made.
This study put two design approaches through the same measurement. The first was User Centered Design, which builds decisions around what users say and do. The second was Material Design Guidelines, a published set of interface rules covering layout, depth, motion, and typography.
User Centered Design starts from evidence about the people using the site. You observe, you test, you revise, and the layout follows from what you find. The strength is fit. The cost is that every decision has to be earned through research.
Material Design Guidelines start from a shared specification instead. The strength is consistency and speed, since the rules already answer most layout questions. The risk is that a specification knows nothing about your particular users.
On tablet and smartphone, both approaches improved the effectiveness and efficiency of content delivery. Neither was wasted effort.
The split appeared in one place. For pages built in a three column layout, Material Design Guidelines delivered a better usability improvement than User Centered Design on the smartphone, specifically for content delivery efficiency.
That is a narrow result, and the authors present it as such. It does not say that guidelines beat user research in general. It says that for one layout style, on one class of device, a published specification closed more of the gap than a research led process did.
The practical use is not to pick a winner. It is to notice that a three column page on a phone is a hard case, and that a codified set of layout rules handles that particular case well.
Pinandito et al. (2017). Analysis of web content delivery effectiveness and efficiency in responsive web design using material design guidelines and User Centered Design. 2017 International Conference on Sustainable Information Engineering and Technology (SIET).
