Each city bidding on the Olympics has an Edge...
For Tokyo: The Government will take on all cost overruns. And the games will be green! The plan is to install large solar panels on the stadium.
Madrid: Claims to be the safest choice, as 77% of the facilities and venues it would require are already built or currently under construction. Makes sense. "Madrid deserves the Games for three reasons: unanimous support from its citizens, nearly all of the installations are finished and organizational experience," former IOC president Juan Antonio Samaranch said.
Chicago: Word has it Obama wants it there... which alone could even get your average Brazilian to vote for it being there, seriously! (Not that they get a vote, of course... I'm just sayin'). Other bonuses - it's charming lakefront, US olympic games typically garner more funds raised by sponsorships, TV money, etc.
Rio: Plans to use facilities from the 2007 Pan American Games as well as the new and renovated venues from hosting the 2014 World Cup. Brazil's claim it has not been hit as hard as other nations by the economic crisis. The fact that the Olympics have never been held in South America. The natural beauty, youth, energy, diversity and splendor of the city. Here's something funny from a member of Brazil's Olympic Commitee: "Barack Obama is more Rio than he is Chicago," Osorio said. "We are the ones saying 'Yes we can.' We are the city of change."
Of course, every venue or city has challenges as well!
Tokyo's: Include having hosted before (in 1964).
Madrid's: It is notable that Madrid recently bid on the 2012 games, which of course went to London, and would mean two consecutive summer Olympic Games in Europe.
Chicago's: The city won't provide international officials with the kind of safety net they want—a blanket government financial guarantee... I'm not sure that any of the cities are providing this, though.
Rio's are of course its infrastructure and crime issues. The fact that Doha actually scored higher on the initial bid process, but Rio squeaked in by default as Doha was vetoed by judges because of how high the temperature is there in the summer. The high projected cost of Brazilian games ($14.4 BILLION)
The big decision/announcement of course takes place October 2!