Bush did business with Bin Laden's bankers while Kerry was fighting to shut it down to terrorist and drug connections.
Long before September 11, 2001, George W. Bush got a 25 million dollar loan from the same bankers that dealt with bin Laden and Saddam Hussein, while John Kerry was fighting to stop this bank's global laundering of money for drug lords and terrorists. John Kerry shut it down. He's been fighting terrorism at its roots since before George Bush ran for office.
"The Bank of Credit and Commerce International was an institution of Middle East origins whose employees asked few questions of their wealthy and powerful customers, making it a favorite of arms merchants, drug dealers, such as Noriega, and intelligence agencies," according to the Boston Globe bio of Kerry. "At the CIA, which sometimes used the bank to launder its own activities, it was known as 'Bank of Crooks and Criminals.'"
In the late 80's, Bush got a loan for $25 million for his failing oil company, Harkin, from a Saudi banker who dealt through BCCI, thereby joining its other customers such as Noriega, Hussein and Osama bin Laden.
At the same time, Kerry was working to investigate it. He used his senate committee powers to shut down this fraudulent banking operation against great opposition from prominent people on both sides of the aisle, including some Democrats who had become involved.
(Kerry came across the bank's shadowy activities, btw, while investigating the Iran-contra scandal, and pursued it.)
Follow the Money is one of the best summaries.