Paul opposes the war on drugs and has said repeatedly he would pardon all non-violent drug offendors as president. Can you imagine Barr ever doing such a thing? When questioned by Stossel on whether a state government should regulate heroin or prostitution, Paul said no. Compare that to Barr, who supports the war on drugs and other victimless crimes (opposition to which has always been a crucial part of libertarianism).
Paul supports a non-interventionist foreign policy. Barr wants to invade Latin America (to expand the war on drugs) and antagonize Iran. Barr has also criticized Obama for wanting to talk with foreign leaders.
Paul wants to eliminate the income tax. Barr just wants to shuffle it around, with the FraudTax. Barr talks a good game on civil liberties, but Paul has the record to back it up. I could go on and on. The point is, Barr is nowhere even close to being as libertarian as Ron Paul, even with Paul running as a damn Republican!
Bob Barr is simply a fraud that is able to con a bunch of gullible and confused “libertarians” into believing he is actually a Libertarian.