Arabica Arabica trees grow best at high altitudes (around 1000-2000 meters) and in mild temperatures. The trees are delicate and quite susceptible to attacks by pests and disease. Because the trees are harder to cultivate, Arabica beans tend to be more expensive. Arabica coffee is usually described as smoother and sometimes slightly acidic, and it is also lower in caffeine.
Robusta As the name implies, Robusta trees are robust and much more resistant to disease than Arabica trees. They also grow best at warmer temperatures and lower altitudes (0-700 meters). Because the trees are easier to grow, are more disease-resistant, and because they produce a higher yield of coffee beans; Robusta beans tend to be less expensive than Arabica beans. Their taste is generally described as being full-bodied, often bitter or too strong. And they have a higher caffeine content.
Arabica or Robusta. Which is better? Because of its bitterness, 100% Robusta coffee is rarely used, except in instant coffees. Italian coffee culture in particular uses blends of Arabica and some Robusta, with Robusta usually accounting for between 10% to 50% of the blend. When roasted well, Robusta beans can provide body and strength that are missing from pure Arabica coffees. They also help give espresso a nice crema.
Unfortunately for Robusta beans, they are often produced cheaply, resulting in low-quality beans. Further, they are often under-roasted which lowers the quality even more, but saves money as less of the bean is lost in roasting. Because of these practices, Robusta coffee has received a bad reputation.
When high-quality beans are roaster and blended well, Robusta coffee contributes to a fabulous espresso experience!