Or, a comparison of the different extras on different versions of the Avengers DVD.

Sharing the love so you know which version you'd like to buy of the movie. Also, keep in mind that this is the region 1 DVD/Blu-ray, and I'm using the Canadian iTunes, so other iTunes stores may vary. I'm personally going to buy the iTunes version.

Marvel's The Avengers
Release date: September 25, 2012
Format/Disc #: 1 DVD Disc
Digital copies: No
Digital Album Download: No
Commentaries: Audio Commentary by Director Joss Whedon
Featurettes:
- “Assembling the Ultimate Team”
Deleted Scenes: None
Other Features: None

Marvel's The Avengers (Two-Disc Blu-ray/DVD Combo in DVD Packaging)
Release Date: September 25, 2012
Format/Disc #: Two Total: 1 Blu-ray and 1 DVD Disc
Digital Copies: No
Digital Album Download: No
Commentaries: Same as DVD
Featurettes:
- “Assembling the Ultimate Team”
- “A Visual Journey”
Deleted Scenes:
- Alternate Opening - Maria Hill Interrogation
- Extended Scene - Loki & Barton Strategize
- Steve Rogers - Man Out of Time
- Nick Fury & World Security Council
- Extended Viaduct Fight - Raw Footage
- Fury & Hill Discuss the World Security Council
- Extended Scene - Banner and Security Guard
- Alternate Ending - Maria Hill Interrogation
Other Features:
- Marvel One-Shot: Item 47
- Second screen
- Gag reel
- Soundgarden music video - “Live to Rise”

Marvel's The Avengers (Two-Disc Blu-ray/DVD Combo in Blu-ray Packaging)
Release Date: September 25, 2012
Format/Disc #: Two Total: 1 Blu-ray and 1 DVD Disc
Digital Copies: No
Digital Album Download: No
Commentaries: Same as DVD
Featurettes: Same as Two-Disc Blu-ray/DVD Combo
Deleted Scenes: Same as Two-Disc Blu-ray/DVD Combo
Other Features: Same as Two-Disc Blu-ray/DVD Combo

Marvel's The Avengers (Four-Disc Combo: Blu-ray 3D/Blu-ray/DVD + Digital Copy + Digital Music Download)
Release Date: September 25, 2012
Format/Disc #: Four Total: 1 Blu-ray 3D, 1 Blu-ray, 1 DVD and 1 Digital Copy Disc
Digital Copies: Yes
Digital Album Download: Yes, see full track list in Special Features section below
Commentaries: Same as DVD
Featurettes: Same as Two-Disc Blu-ray/DVD Combo
Deleted Scenes: Same as Two-Disc Blu-ray/DVD Combo
Other Features: Same as Two-Disc Blu-ray/DVD Combo

Marvel Cinematic Universe: Phase One - Avengers Assembled (10-Disc Limited Edition Six-Movie Collector's Set)
Release Date: September 25, 2012
Format/Disc #: 10 Discs Total
Digital Copies: To Be Announced
Digital Album Download: TBA
Commentaries: TBA
Featurettes: TBA
Deleted Scenes: TBA
Other Features: TBA

iTunes
Release Date: September 25, 2012
Format/Disc #: Digital
Extras:
- Marvel One-Shot - Item 47
- Marvel's First Ever Gag Reel
- The Avengers Initiative: A Marvel Second Screen Experience
- "Live to Rise" Soundgarden Music Video
- Assembling the Ultimate Team: A Visual Journey
- Deleted Scenes (I'm assuming these are the same ones as in the physical copies)