I've not yet done a comparative with 2 texts, but I have done a few with a cartoon and 1 article.
Personally, I go through the article, as it is mostly the main piece, and I choose key arguments that the author writes about. I pick three, and I use these to form the my 3 body paragraphs in my essay. Then, with the cartoon, I try to choose which argument/idea this links with the best, and I analyse the cartoon in that body paragraph. This doesn't work for everything though. I don't usually anaylse the intro though. If I feel like the cartoon and text don't relate to each other at all, I'd do 2 paragraphs anaylsing 2 key points by the text, and 1 paragraph for the cartoon.
When I think of ideas, I think of key arguments.
This is what works for me, and what my teachers expect, so its definetely not the only/best way to go.
Hope this helps a bit though! Let me know if you have any questions