When it comes to taxes, fiscal priorities, rights for individuals, foreign policy, crime and punishment, and of course social issues they are very different and in most cases take the opposite approach.
For example, Republicans want lower taxes for the wealthy while Democrats want lower taxes for the lower and middle classes. Republicans want to restrict individuals rights - especially for non-christian white males, Democrats don't. Republicans favor heavy handed punishment including capital punishment, Democrats favor rehabilitation and a ban on capital punishment. Republicans want to blow up the national debt through tax breaks and pork, Democrats want to control the debt through responsible spending and investments. Republicans want to stop investment in education and science while Democrats want to increase investment in these areas. These are all very real and not just aesthetics.