Okay, I didn't like this film as much as I used to (a rival suitor at Portman's hospital is worthless, a brief bit with Abby Elliott is sloppily handled), but I'd still absolutely rate it higher than Friends With Benefits. No Strings Attached has a better and more grounded emotional conflict throughout, a sharper script, and an unreasonably good cast (Jake M. Johnson, Greta Gerwig, Mindy Kaling, Lake Bell, Ludacris, Kevin Kline, Olivia Thirlby, Elliott). The only weak link is Kutcher, who is serviceable but easily the clunkiest element of the ensemble.
Both Definitely, Maybe and No Strings Attached have scenes where Kevin Kline is in the hospital, and Friends With Benefits doesn't. Clearly, this is a key secret ingredient.