I also got a call from Ming Wai offering a pm class. I have declined becasue I don't like the environment of the school (and also because I have an am offer from other school).
In my view, I only want my daughter to learn discpline and be independent in PN class. I think Hop Yat Tong is a better than Ming Wai in this aspect. The playground of Hop Yat Tong is also bigger than Ming Wai. Unless you plan to go to Int'l school, most of the good K1 schools conduct their interviews in Cantonese, I don't think Ming Wai will have an advantage for preparing for K1 interviews.