Cordless drills are often compared mainly by voltage, but voltage alone does not tell you whether a drill is suitable for a particular job.
A compact 12V drill may be a better choice for furniture assembly and light household work, while heavier drilling and construction tasks may justify an 18V or 20V-class platform.
This guide explains the specifications that actually affect performance, including torque, battery capacity, chuck size, motor type and compatibility with other tools in the same battery system.