Publishing: quality vs. quantity
A direct answer for your question would be that quality would be better than quantity in this case.

By a larger paper would not always be of a better quality than a smaller one. But if you mean a paper with more extensive research and collation of results obtained from rigorous time consuming experimentation, then yes. Such a paper would carry more positive impact than multiple smaller ones that you could use just for the count. This is from the viewpoint of your advisor.

Some may prefer increasing the number of publications, but it would only matter if they are published in reputable journals, in other words, if they all hold quality (at least in most cases).

So if you intend to sacrifice quality for quantity, my honest opinion would be the same as your advisor's.