Comparing advantages and disadvantages of primary, secondary and tertiary sources cannot be done in a one-dimensional way. One type of source is not by definition worse or better than another type. It depends on context, what you're trying to use the source for, sound editorial judgement etc.

There are techniques with which to compare advantages and disadvantages in a multi-dimensional way, that provide an easy to follow overview. The model used here is borrowed from business planning, SWOT analysis. Each type of source has its specific advantages and disadvantages, the idea is to exploit Strengths and Opportunities to the maximum, avoiding Weaknesses and Threats. The analyses below highlight only major directions.

Even non-for-profit organisations like Wikipedia are businesses for which a SWOT analysis makes sense. The general objective is to improve Wikipedia. The SWOT analyses below are however "product placement" SWOTS, not analyses of the organisation as a whole. The finite business objective for which these SWOT analyses are presented below is to provide proper sourcing for all articles, which is a subset of the general goal of improving the encyclopedia by implementing core content policies like WP:V. Three "products" are presented to the "customers" (= Wikipedia editors) concurrently in order to reach that business goal. Below are reasons for which to choose source types depending on circumstances.