Sponsored Products: the workhorse
Sponsored Products are available to every seller, promote single listings in search and on product pages, and are where most sellers spend most of their budget. Start here — it is the foundation of Amazon PPC.
Sponsored Brands: the top of the page
Sponsored Brands show your logo, a headline and several products across the top of search, and can send shoppers to your Store. They need Brand Registry and suit branded and category searches more than the long tail.
When to use which
Use Sponsored Products to convert demand across all your keywords; add Sponsored Brands once you have Brand Registry and want to own the top of the page and defend your brand searches. Run together, they cover more of the funnel; run carelessly, they overlap and waste budget.
Run them as a team
The trick is coordination so they do not cannibalize each other. AIAdKing optimizes Sponsored Products, Brands and Display in one nightly cycle, so spend is balanced across all three rather than competing.