The short answer is it depends. The long answer is it depends on what you want to build. You see, comparing Arduino and Raspberry Pi is like comparing a Swiss army knife with a toolbox. Arduino is essentially a microcontroller and as the term implies, it is a microchip on a circuit board that is mainly used to control things. Raspberry Pi, on the other hand, is a microcomputer. It does more or less the stuff that your computer can do albeit with lower computing power.
So, if you’re looking to build a small-scale or simple electronics project to control some components, you should be using an Arduino. If you’re developing something that requires more processing power such as data or image processing or robotics, you should consider Raspberry Pi.
Generally, Raspberry Pi can do what Arduino could but you may not need the complexity of Raspberry.