I suppose the biggest policy disagreement today centers on how to make the world a peaceful, free place in places where peace and political freedom are virtually unknown.
Conservatives generally support charging in, tearing down the old system, and putting Jeffersonian democracy in it's place.
Liberals support spreading democracy around the world, but via methods other than invasion. Most despotic countries have strong democratic movements which are supressed by the government, often with support and aid from the US government. Liberals would prefer to suspend aid to dictatorial regimes and let countries choose their own fate rather than impose a foreign ideology.
