Significant differences between the two major parties

Some people argue that there are no significant differences between the two major parties. Backing up your perspective with appropriate sources, what are the major differences and similarities in the views of the Democratic and Republican parties (e.g., this review of party platforms, 1856-2016 www.washingtonpost.com/graphics/politics/2016-election/conventions/party-platform-evolution/)? What are the primary areas of difference between contemporary Democrats and Republicans? (e.g., taxes, abortion, guns, LGBTQ rights, etc.) How are the two parties similar? What are the consequences of these patterns for voters and election outcomes? For policy outcomes?