Collisions lie at the core of two of this week’s major DVD releases: the first season of TV’s “Lost” and Paul Haggis’ critically acclaimed film “Crash.” Both deal with accidents – in “Lost,” a plane wreck; in “Crash,” a series of vehicular smashups and racial conflicts. Both deliver completely compelling viewing; but DVD-wise, only one provides a complete package absolutely worth purchasing.

That would be “Lost,” which expands on all the suspense and mystery of the series with scads of extra features. For those who haven’t joined the cult of Sawyer-and-Sayid worshippers, the seven-disc set provides an excellent introduction to this cast of appealing survivors, none of whom bears any resemblance to Richard Hatch of “Survivor” infamy.

With panoramic views of the tropical island setting and convincing special effects, “Lost” has a more cinematic feel than most TV shows. That’s highly apparent on DVD: Presented in widescreen format, the picture looks practically as sharp as it does when ABC broadcasts it in high-definition.

Fans of “Lost” will want to revisit the episodes before the second season’s premiere on Sept. 21 if only to again comb each scene for clues to certain unanswered questions. (Seriously, what is the deal with that hatch?) But they also will relish the opportunity to dig into the extras, which are superb, except for the sometimes superfluous commentary tracks.

Disc seven is devoted to nothing but bonus features, including several behind-the-scenes featurettes, 13 cast audition tapes, a half-hour look at the making of the pilot, 13 deleted scenes, bloopers and an excerpt from a panel discussion at the Museum of Television & Radio. One complaint: None of the extras delves into the show’s numerology, which has become the source of much fan fascination. Then again, that’s what The “Lost” Numbers Blog (http://thelostnumbers.blogspot.com) is for.

Crash

The “Lost” crew – including creator J.J. Abrams, who also gave birth to TV’s “Alias” – clearly put a lot of thought into what should be included in this collection. It shows, and it’s why “Lost,” unlike many TV shows, winds up with a DVD that matches the quality of the series itself.

Unfortunately, “Crash,” a terrific film, comes to DVD with a scarcity of bonus features. An indie with a high-caliber cast, the movie’s small budget probably didn’t allow for the creation of in-depth DVD peeks into the filmmaking process. Instead, the disc includes one short, behind-the-scenes featurette and a commentary track by writer-director Haggis, producer-co-writer Bobby Moresco and producer-star Don Cheadle.

The three spend much of their time complimenting the fine performances by the actors. Of course, they’re right: Matt Dillon does “deliver big time” and Ryan Phillippe is “great in this.” But it’s not particularly enlightening to hear. Of greater interest are the other tidbits Haggis mentions, such as the fact that “Crash” was shot in just 36 days, or that the part played so commandingly by Terrence Howard was originally written for Forest Whitaker.

With its multifaceted characters and honest look at race relations in America, “Crash” is a must-see movie. But those who feel they must purchase the DVD may want to hold off. If it garners a few Academy Award nominations – and early buzz indicates that it will – a special edition might very well come to pass.

Best “Lost” Airplane Bonus: The featurette “Designing a Disaster” shares fascinating details about doomed Oceanic Air Flight 815, re-created for the show with a retired Lockheed L1011 that had to be taken apart, flown to the set in Oahu and reassembled to create a crash site. If that aviation information doesn’t fascinate, “Welcome to Oahu: The Making of the Pilot” goes a step further by revealing that pieces of the wreckage were used as instruments that can be heard, faintly, during the show’s musical score. Now that’s recycling.

Lost “Lost” Bonus: I’m sure there are more Easter eggs buried in this massive set. But so far, I’ve only unearthed one: Click on the words “Disc 7” on the bonus features disc and you can see an alternate opening to the show.