Question: What is the difference between Joss Whedon and Sylvester Stallone as directors? 

Context articles: The Expendables 2
Joss Whedon's unrealized projects
Sylvester Stallone
Angel: After the Fall
Serenity (comics)
Whedonesque.com
Joss Whedon
Jed Whedon
The Expendables 3
Pilot (Agents of S.H.I.E.L.D.)

The Expendables 2 is a 2012 American ensemble action film directed by Simon West, written by Richard Wenk and Sylvester Stallone and based on a story by Ken Kaufman, David Agosto and Wenk.
 Brian Tyler returned to score the film.
 It is the sequel to the 2010 action film "The Expendables", and stars Sylvester Stallone, Jason Statham, Jet Li, Dolph Lundgren, Chuck Norris, Terry Crews, Randy Couture, Liam Hemsworth, Jean-Claude Van Damme, Bruce Willis, and Arnold Schwarzenegger.
 The story follows the mercenary group known as "the Expendables" as they undertake a seemingly simple mission which evolves into a quest for revenge against rival mercenary Jean Vilain, who murdered one of their own and threatens the world with a deadly weapon.
 It is the second installment in "The Expendables" film series.
The following is a list of unproduced Joss Whedon projects in roughly chronological order.
 During his long career, American film director Joss Whedon has worked on a number of projects which never progressed beyond the pre-production stage under his direction.
 Some of these projects, are officially cancelled or fell in development hell.
Michael Sylvester "Sly" Gardenzio Stallone ( ; ] ; born July 6, 1946) is an American actor and filmmaker.
 He is well known for his Hollywood action roles, including boxer Rocky Balboa, the title character of the "Rocky" series' seven films from 1976 to 2015; soldier John Rambo from the four "Rambo" films, released between 1982 and 2008; and Barney Ross in the three "The Expendables" films from 2010 to 2014.
 He wrote or co-wrote most of the 14 films in all three franchises, and directed many of the films.
Angel: After the Fall is a comic book published by IDW Publishing.
 Written by Brian Lynch and plotted with Joss Whedon, the series is a canonical continuation of the "Angel" television series, and follows the events of that show's final season.
 "Angel: After the Fall" was prompted by IDW Publishing and Joss Whedon after the success of Dark Horse Comics' "Buffy the Vampire Slayer Season Eight" which is the official comic continuation of "Angel"'s mothershow, "Buffy the Vampire Slayer".
 "Angel: After the Fall" sees the heroic vampire, Angel, coping with the apocalyptic aftermath of the television series after he took over and subsequently betrayed the demonic law firm, Wolfram & Hart.
 The city of Los Angeles has since been sent to hell by Wolfram & Hart as a result of Angel's actions.
 The series follows his attempts to rescue the people he has sworn to protect.
 The first issue was released on November 21, 2007.
Several comic book stories have been released under the Serenity title, set in the fictional universe created for Joss Whedon's "Firefly" television series and "Serenity" film, and which are considered canon.
 As of 2014, eight "Serenity" stories have been published.
 Written by Joss Whedon and Brett Matthews, and illustrated by Will Conrad, the first miniseries, "Those Left Behind", was created as a bridge between the events of the series and film.
 "Those Left Behind" was popular: the first issue was the highest-selling comic published by Dark Horse Comics since the release of "Buffy Season 8" in 2007, while the trade paperback is still one of the highest ranking items by sale quantity from that company.
 In early 2008, a second miniseries was released.
 Titled "Better Days", it was set before "Those Left Behind", with the storyline based around a heist that went in the characters' favor.
 In addition to the miniseries, a one-shot comic written by Jim Krueger and titled "The Other Half" was released in the August 2008 issue of "Dark Horse Presents".
Whedonesque.com (also referred to as Whedonesque) is a collaborative weblog devoted to the works of Joss Whedon.
 Submissions of new content ended on August 21, 2017, following the publication of an open letter by Whedon's ex-wife Kai Cole.
 At its inception in 2002, Whedonesque covered "Buffy the Vampire Slayer" and "Angel", but expanded to follow Whedon's professional output, as well as the careers of cast and crew associated with Whedon projects.
 Since 2004, the site has been recognized in other media outlets by awards and citations of Whedon's writings originally posted to Whedonesque.
Joseph Hill Whedon ( ; born June 23, 1964) is an American screenwriter, director, producer, comic book writer, and composer.
 He is the founder of Mutant Enemy Productions and co-founder of Bellwether Pictures, and is best known as the creator of the television series "Buffy the Vampire Slayer" (1997–2003), "Angel" (1999–2004), "Firefly" (2002), "Dollhouse" (2009–10) and "Agents of S.H.I.E.L.D." (from 2013).
Jed Tucker Whedon (born July 18, 1974) is an American screenwriter and musician, and the son of screenwriter Tom Whedon, grandson of screenwriter John Whedon, and the brother of screenwriter Zack Whedon and producer/director/writer Joss Whedon.
The Expendables 3 (sometimes stylized as The Expendables III) is a 2014 American action film directed by Patrick Hughes and written by Creighton Rothenberger, Katrin Benedikt and Sylvester Stallone.
 It is the third installment in "The Expendables" film series and the sequel to "The Expendables" (2010) and "The Expendables 2" (2012).
 The film features an ensemble cast, including Sylvester Stallone, Jason Statham, Antonio Banderas, Jet Li, Wesley Snipes, Dolph Lundgren, Kelsey Grammer, Randy Couture, Terry Crews, Kellan Lutz, Ronda Rousey, Glen Powell, Victor Ortiz, Mel Gibson, Harrison Ford, and Arnold Schwarzenegger.
"Pilot" is the pilot and first episode of the first season of the American television series "Agents of S.H.I.E.L.D.", based on the Marvel Comics organization S.H.I.E.L.D. (Strategic Homeland Intervention, Enforcement and Logistics Division), revolving around the character of Phil Coulson and his team of S.H.I.E.L.D. agents as they investigate a super-powered man and a hacktivist group.
 It is the first television episode to be set in the Marvel Cinematic Universe (MCU), sharing continuity with the films of the franchise.
 The episode was written by series creators Joss Whedon, Jed Whedon, and Maurissa Tancharoen, and was directed by Joss Whedon.