COMPARING ARABICA AND ROBUSTA. This post on the enjoyjava site lists 11 differences between arabica and robusta. Arabica contains more sugar. Robusta contains more caffeine and, since caffeine is bitter, robusta is more bitter.
“Arabica has a more pleasant flavor than robusta. The flavor of arabica is described as being rich with hints of chocolate, nuts, fruit and berries. Robusta on the other hand, as tasting bitter, earthy, and rubbery.” Robusta is lower in acidity “which lends to the woody or burnt rubber flavor.”