Saucepan or Sauteuse pan?
Cook's Illustrated inferred (can't find link; only have a printout now) that the Sauteuse can function as a saucepan as well as allow for faster reduction (greater liquid surface area compared to heating area) and allows whisks to more easily access the interior surfaces. (They still listed top choices for both.) It looks like a sauteuse pan is also called a saucier. The link appears to reference the top choices by CI.
Any thoughts as to "Why buy both?" or "Is one better (i.e., more multi-functional) than the other?"
Here is a link that might be useful: Cook's Illustrated Essential Cookware (Amazon)