Given the background description of some cooking related query, summarize the question into a title

When making e.g. spaghetti sauce, do I:first sweat the onions and then add the minced meat?first brown the minced meat and then add the onions?do both at the same time but in different pans and add them together afterwards?What are the advantages of preferring one of the options over the others?
First onion or first minced meat?