It frustrates me greatly to see comments like this. It's worth taking a moment to even briefly skim the official platforms of the two major parties. They are profoundly different on a enormous range of substantive issues and policies.
Perhaps there are some issues on which the two parties agree, and certainly there are many political positions which neither party represents. That hardly means that the two parties are "not that different."
However, it probably fair to say both parties have most candidates skewed to the middle on many of those issues. Lining up strongly with the party on all of those things doesn't win elections usually. And it's also fair to say both parties have members that will betray those base positions for wealth or power.
I can see why someone would call them similar based on frustration with a two party system that rewards moderates.
I'm astounded that there are blacks living in ghettos but Nancy Pelosi shuts Govt down for people who are pondered to by speaking Spanish but paraded as having known no other culture and assimilated.