The Acaia Pearl is designed for home and shop manual brewing, where the Acaia Lunar is designed for preparing espresso on the drip tray of an espresso machine. It really depends on what kind of brewing you plan to perform.
Both scales can technically function as an espresso scale or a manual brewing scale, but their features and size were designed to meet different needs.
The Pearl is a sleek manual brewing scale that meets the desires of those design-obsessed baristas and coffee shop owners while meeting the needs of those coffee enthusiasts weighing to a tenth of a gram. It is an ideal scale for those wishing to regularly make great pour-over coffee, with a number of different built-in modes and abilities to aid in brewing.
The Lunar is designed with industrial balance technology to deliver the highest accuracy and connectivity while being able to withstand the environment of a commercial espresso machine’s drip tray. The 10.5 x 10.5 cm anodized aluminum platform is sealed against liquid entry, and the electronics within have a protective spray coating to shield against moisture.