Think I'd have to go with Coen Bros. over Tarantino, simply because they have more 5-star (in my opinion) films to their credit than Mr. T.
Coens have:
Blood Simple
Miller's Crossing
Barton Fink
Fargo
The Big Lebowski
O' Brother Where Art Thou
Burn After Reading
No Country for Old Men
Tarantino has:
Reservoir Dogs
Pulp Fiction
Jackie Brown
KILL BILL (counting both volumes as one movie; get over it
)
Inglorious Basterds
Django Unchained
8-6 Coens.
Of course, the Coens have more shitty (Intolerable Cruelty), and meh/so-so (Hudsucker Proxy, A Serious Man) movies than Tarantino, who has... well, none. I haven't seen Death Proof, but I doubt it's outright
shitty (probably quite fun, but not likely a 5-star work or a masterpiece).
I also haven't seen a couple Coens films (Hail Caesar!, Llewin Davis), but even if they're total shit, it won't take away from the cinematic mastery of their best films. I think Tarantino is a bit more singular... he's synthesized a style entirely his own out of Scorcese, Shaw Brothers, Coppola, Don Siegel, the spaghetti westerns and Blacksploitation films of the '70s, and a host of other stylistic and narrative elements from the history of film. With this he's managed to become more than just a revisionist, bringing an ultra-modern, often meta flare to "classic" filmmaking. He's more iconic and iconoclastic than the Coens.
The Coens are probably more adept at nuts and bolts filmmaking, having mastered black comedy and quiet tension on both script and screen. Despite being equally oddball when they're just being themselves, I'd say the Coens are more "mainstream" -- they're utterly absurd, but they also have a knack for making more generalized *movie* movies, if that makes sense. Like No Country and True Grit. Just total crowd pleasers that anyone can appreciate. I'm sure Tarantino has this in his skill set somewhere, but he's clearly not interested in making that kind of film.
The Coens are more masters of a craft than flippers of a script. The opposite is true for Tarantino, though he is certainly a master as well.
Blech. Not sure who I outright prefer, but statistically I'd have to go with the Coens. For now.
... 'Cause I know you were all just
dying to know.