I would prefer to rank the subcategories, because they are of much more value for the user. Will this also mean that if I have 20 subcategories they are less likely to rank than when I have only 10 ?
I do not think the answer is that simple. One of reasons why subcategories *may* rank better is that they will have the majority of links going out to the relevant articles for this subcategory (+ only 8 links out to other top categories). This should result in the subcategory focus tighter to the subject. It also means that articles within a subcategory (and links to these articles/link anchors) are more related to each other, helping with the focus.
Whilst 10 subcategories may have larger portion of the link juice coming from its main category, if the focus of each subcategory is too wide for a particular set of keywords, they may in fact not rank better than more granular subcategories despite receiving more link juice.
So the right answer would be: look at your site architecture and create that many subcategories as it makes sense for the focus of each subcategory.
And in all that don't forget the easy and intuitive navigation for your visitors!