How to describe my favourite scientific publication? And why I have to do that?
I think purpose of that question while applying to graduate program is to check your judgment or thought process. It will be similar to writing statement of purpose (SOP) where you try to justify why do you choose any institute/program/career etc. I think, any paper (research or review) is fine as far as you give reasonable answer to their question about "why do you like that publication". 

There might be many different answers to that questions, One might like following things from that paper 


The way research has done
The way authors have interpreted results
The way connections have made to other problems
The way they have formulated model from existing information (This is generally done in reviews)
The way authors has provoked future questions 


Most important thing you should mention in your answer that how this paper has helped you in any way. For example, one might say, I liked the way authors have used very general methods cleverly to answer some difficult question which changed your perception about solving difficult questions with simple methods. In case of review, you can say how authors have used many well established and new concepts to make current model. This helped you in understanding some complex concept.