There is a distinct taste difference between bourbon and sour mash...There is a distinct taste difference between rye and bourbon and sour mash.
Pure Canadian rye whiskey is probably the smoothest whiskey ever...
The flavor difference between rye and bourbon is due to different content in the mash bills. The flavor difference between bourbon and Tennessee whiskey is mostly due to the latter's filtering (depending on which bourbon you're comparing).
There's a *lot* of variance in bourbons. "Traditional" bourbons use about 70 percent corn and then roughly equal amounts of rye and barley. There are also "high-rye" bourbons and "wheated" bourbons, each of which has a different mash bill and flavor profile.
I've been glad to see straight rye whiskies making a comeback over the past few years; Prohibition nearly killed it off in the U.S.