Webflyer.com has a feature called Head2Head, where you can compare any two programs next to each such that the features, pros, and cons of each are side by side.
I contributed descriptions of Continental OnePass and United Mileage Plus for them. With Continental I made substantial revisions to what was already there, for United I started from scratch.
I’d appeciate comments or thoughts from readers here about whether I was fair to the programs, whether I should have highlighted something I left off, etc.
Last I looked (a few year ago), United allowed both layovers in each direction and open jaw award tickets on Star Alliance carriers. Most other programs allow either a layover or an open jaw, not both.
United offers one stopover OR an open jaw.
American offers a stopover AND an open jaw.