The short answer
Arabica is sweeter, more complex, and less bitter; Robusta is stronger, harsher, and has nearly twice the caffeine. Arabica accounts for around 60% of world production and dominates specialty coffee, while Robusta is prized for its punchy body, crema, and lower cost — common in espresso blends and instant coffee.
Neither is simply "better." Arabica wins on nuance; Robusta wins on strength, body, and value.
How they differ in the cup
• Flavor: Arabica has sweetness, fruit, and floral or chocolate notes. Robusta is bolder, woodier, and more bitter, often described as rubbery or grainy.
• Caffeine: Robusta has roughly 2.2% caffeine by weight versus about 1.2% for Arabica — nearly double, which also makes it more pest-resistant.
• Body and crema: Robusta brings heavier body and thicker crema, which is why a little is often added to espresso blends.
• Price: Arabica costs more to grow and buy; Robusta is the value species.
When to choose each
Choose Arabica for pour over, drip, and anytime you want to taste origin character and sweetness — it is what most specialty coffee and single origins are. Choose or seek out some Robusta if you want maximum caffeine, a thicker espresso crema, or a traditional bold, bitter cup (many Italian and Vietnamese styles use it).
Most quality bags are 100% Arabica; espresso blends sometimes add 10 to 20% Robusta for body. Check your caffeine intake if you switch to a Robusta-heavy blend, since the jump is significant.