For this article, I tested ten professional-grade tools from nine different manufacturers: Bosch, DeWalt, Hilti, Hitachi, Makita, Metabo, Milwaukee, Panasonic, and Porter-Cable. I chose to focus on the 14.4-volt tools because they're a reasonable compromise between the lighter 12-volt and the heavier 18- and 24-volt models. Tradespeople seem to agree, because they buy more 14.4-volt drill-drivers than any other cordless tool.
We included three 15.6-volt drills from companies that don't make 14.4-volt tools. It's reasonable to include them because they have similar specs and performance; the only difference is an extra cell in the 15.6-volt battery packs.
to read the full article.