Results are bound to change because of the perspectives. The amount of articles as well, considering that in the Article perspective, the CPI takes the published articles within a given timeframe (which will have one threshold). And in the Traffic one, it will focus on all of those which had any traffic in the given period (creating a different threshold). If you also add filtering on top of that, the data pool is different (and since they are compared among each other), thus are the results.
Article-oriented perspective allows you to analyse your website by putting your content in the focus. CPI here is always calculated on the article level and its values are distributed across authors, sections, and topics by taking in mind your chosen time period.
Traffic-oriented perspective allows you to analyse your article, section, topic or author performance by putting the traffic they gained in the focus, and CPI is always calculated depending on the chosen dimension and set time period.