The remarkable thing about this autumn's high-profile thrillers is that arguably all of them are worth seeing.  The question is, should you run out to catch these films while they're still in theaters, or wait a few months and enjoy them on smaller screens?  One problem may be simply differentiating them—yes, they're all thrillers, but within the genre each has its own flavor.  The intent of the below capsules is to provide you with some info to make decisions based upon your own tastes and preferences.

American Gangster:
What is it really?  An atmospheric cops-and-robbers epic with only a few isolated sequences containing genuine thrills.  Think of it as combining the dramatic arch of the archetypal gangster film (e.g., Scarface, 1932, 1983) with the self-conscious stylization found in a crime "saga" such as Heat (1995).  Also similar to, in terms of its focus on Vietnam-era crime, James Ellroy's novels American Tabloid and The Cold Six Thousand.
Why run?  Ridley Scott's storytelling—efficient and rarely off the mark; and for fans of Scott, his signature visual tropes are in full effect.
Why wait?  Again, Ridley Scott's storytelling—very Hollywood, even when it's trying to be "gritty"; and those same Scott's signature visual tropes are often overindulged—we're treated to the sight of gently swirling snow about half a dozen times.  And let's not forget Russell Crowe's elusive New Jersey accent (okay, so maybe it bugged me more than most because I live in Essex County, where his character is from).

Michael Clayton:
What is it really?  Ostensibly a legal thriller but really an outright crime thriller; there are no courtroom scenes—the closest we get is a deposition and even it is interesting for non-legal reasons.  Really a makeover of the classic "paranoid thriller" detailing corporate or government malfeasance, so that in this case the thrills are foregrounded and the "message" is wisely downplayed.
Why run?  Compelling tension starts in the opening scene and never really lets up.  The script is wicked smart, but also not afraid to get its hands dirty:  the dialogue is crisp but this is a movie where people sweat a lot, too, and it shows.
Why wait?  The "twist" at the end is visible from about five miles away.  And the circular narrative structure, although well done, is hardly original at this point.

No Country For Old Men:
What is it really?  A "Western" noir.  The grand pursuit across an unforgiving landscape is right out of Winchester '73 (1950)—or Fargo (1996).  The violent set pieces represent a near-perfect marriage of action choreography/camerawork and editing for maximum suspense.
Why run?  Mercilessly downbeat—a story that does not sell out the truth that it's telling.  Also, a mesmerizing exercise in sheer craft:  ankle-high tracking shots, a haunting use of sound, and direction that gets the most out of its topflight cast.  Pretty much a flawless adaptation of a major work by an author whom I consider to be America's finest genre writer.  And one more thing:  the scariest non-paranormal bad guy you'll see in many a moon.

Why wait?  Um, well, it's mercilessly downbeat.  Be warned:  if you're not really into a "cold" sensibility in your art, you may well develop frostbite from this picture.  In addition, some will find that the events unfold in a dry, even boring manner, perhaps not realizing that it's the lack of music on the soundtrack that largely contributes to this perception.  Also, those who expect conventional closure for a thriller will be sorely disappointed.

Gone Baby Gone:
What is it really?  In many ways an old-fashioned hardboiled mystery rather than a contemporary crime thriller.  It's got a couple of action scenes, but expect the narrative to hinge on the revelation of clues, character development, and a nuanced evocation of time and place—not on a "ticking clock"-type plot as one might expect from the trailers and ads.
Why run?  Extremely solid performances all around, anchored by Casey Affleck's.  And as director, Ben Affleck accomplishes something that's as rare as it is impressive in the thriller genre:  he captures a particular milieu in its granular details while also managing to frame the story events in a Romantic, almost mythic, glow.
Why wait?  The ending is completely preposterous.  It doesn't quite come across as gimmicky, but it's only a step or so removed.  Also, the way that Michelle Monaghan is used is pretty underwhelming for the most part.  Her character, Angie Gennaro, is vivid in Dennis Lehane's source material but here comes across as a barely helpful sidekick—which is a big problem since the denouement tries to derive some of its power from her relationship with the protagonist.

Before The Devil Knows You're Dead:
What is it really?  A suspense flick crossed with a wrenching family drama.  The violence, when it erupts, is shocking.  But don't expect a classic heist plot or a cat-and-mouse style thriller; this one is more about what happens when the mice run around in circles and start gnawing on their own tails.
Why run?  The climax is emotionally devastating due to the same volatile mixture of crime story elements and everyday people just trying to function in extremis:  the result is a tragic tone that, like all good tragedy, you see coming from a long way off but still packs a punch when it gets there.  And the performances, exhibiting a gutty lack of vanity across the board, are tremendous.  Finally, the sure-handed direction from Sidney Lumet makes what he achieves here look deceptively easy.
Why wait?  The movie's intimate scale may be too narrow in its confines for those who prefer their crime dramas to feature cops, mobsters, and other bigger-than-life characters.  Here the emphasis is on the smaller-than-life aspirations of the main players.  In fact, if you're looking for a movie where you can "root" for one or more of the characters, you might want to take a pass.

Bonus DVD Recommendation:  If you just want to stay at home and still catch a topflight thriller, check out Johnny To's Election (2005), recently released on DVD as part of Tartan's "Asia Extreme" line.  To's much-heralded style, which combines no-holds-barred brutality and a glistening sheen on his images, is beautifully shown off here.  Get set for a high-stakes tale of loyalty and betrayal, HK-style.