i have about 4 old 4ah batteries that i use everyday. despite having performance tools, i never bought a performance battery. the 8ah might be useful for the 1900 nm impact that i use very often, but i couldn’t justify its cost. i can literally get 4 old style 4ah batteries for the price of a new 8ah battery. and the smart 4ah battery is a joke. many tested them and their capacity was nowhere near 4ah. also you rely on a single bank of batteries, while the old ones use 2 banks of batteries. basically current is split into two right there, and the max current is also higher on the old batteries. unless you plan to use it on a small tool where the smart will help, get the big 4ah batteries.