In a city that celebrates absurdity, it's fitting that the second international biennale in its history should split into two separate and acrimonious events, with both camps claiming the "biennale" title and asking the public to take sides. Prague Biennale 2, the independent effort set up in a leaky Karlín warehouse after being ousted from the National Gallery, clearly gets the underdog vote. Stickers appearing at the Karlín show call for a boycott of the rival event — the National Gallery's International Biennale of Contemporary Art (IBCA), which is officially sanctioned by the Czech president and the mayor of Prague and generously supported from state coffers.

Good art transcends politics, however, and the art at the National Gallery biennale is impressive, challenging and compelling. If you haven't been there yet, there's still a few days left to see it.

Although the Karlín show bills itself as "the largest art exhibition in Central Europe," the National Gallery's IBCA is bigger, with about twice as many artworks exhibited over twice as much floor space, according to the organizers' figures. Featuring some 800 works by about 400 artists from 20 countries, the IBCA also includes more large-scale pieces such as the massive orange shoeshine kit that Puerto Rican artist Charles Juhasz Alvarado built as a woodshop. Inside, there's a large-as-life wooden horse in an installation that is mysterious, poetic and well-made.

Head curator Tomáš Vlček selected 22 international curators who in turn chose the artists. The show features significant contributions from Chile, Russia, Romania, Croatia, Macedonia and China, among other countries. Through all the sections are united by the theme "Second Sight," the curators interpreted this variously as reimagining human vision, re-forming broken identities or offering perspectives on contemporary life.

A section curated by Jan-Erik Lundström (Sweden) is particularly strong, featuring works that build on one another. Finnish artist Miklos Gaál's photographs make real street scenes look eerily like dioramas. A line of focus moves through the images at a curious angle, making some areas incredibly sharp while others blur out. Also making use of blur are works by Evanthia Tsantila (Greece), who paints overlapping passages that appear abstract until the viewer steps back to see the shapes coalesce.

Another strong section, curated by Marek Schovánek, a Czech artist who lives in Berlin, comments on "human faith in material salvation." Schovánek includes an ingenious work by Lithuanian artist MK Kähne in which sleek black lounge chairs, a wine bar and an audiovisual entertainment center all fold up into a thin, self-contained capsule. Similarly impressive is German artist Markus Krieger's System No. 2, in which hundreds of toy-car motors spin in a suspended electrical web. The web has the pulse and hum of productivity, like a human sweatshop viewed from a distance.

More overtly political works include Unfinished by Swiss artist Isabelle Krieg, a stack of dirty coffee cups that, on closer inspection, reveal likenesses of George Bush, Osama bin Laden and others — a commentary on the United States' unfinished business. Also appreciated is Huong Ngo's Escape Pod Series, an amusing satire on the climate of fear in the United States.

Four sections of Czech visual art include Jiří Georg Dokoupil's intriguing paintings made from candle soot and Jakub Moravek's video installations that invite viewer participation. The largest section of Czech art — curated by National Gallery Director Milan Knížák, a figure at the center of the biennale controversy — is mostly disappointing. The Karlín show features a much stronger section of Czech and Slovak art, with lots of imaginative and humorous works.

The National Gallery's clean, well-lit space undeniably shows off the art better than the warehouse ambiance of its rival. The IBCA's larger budget is apparent in all details of its presentation; even the works themselves look as if they cost far more to produce. In contrast, the Karlín show has an underground feel, not only in the gritty character of its warehouse setting but also in attitude, with in-your-face works such as burning flags, Nazi homoeroticism and disturbing audio. That said, the Karlín works are of a more consistent quality, while the IBCA elicits both louder groans and more enthusiastic wows.

On a high window at Karlín Hall, the Czech art group Kamera skura has painted its commentary on the biennale war: a blue-and-yellow scoreboard reading "0–0." When politics sideline the art, everyone loses. But there's no denying that the battling biennales brought a lot of good art to Prague. And viewers turned out by the thousands for both shows. In the end, though, the competition may have raised the bar for chosen works, and the tension certainly breathed a different kind of life into the exhibitions.