When evaluating the practical efficiency of a pickaxe, two things should be taken into consideration: the amount of hits required (from high pickaxe power); as well as the ticks per hit from low mining speed. The use time attribute can safely be disregarded, because it reflects the weapon swing/animation and is not related to the hits for mining.
Pickaxes can use modifiers that increase speed, like Quick and Light. Accessories with a melee speed bonus will only affect the weapon swing, and will not affect mining hits (by affecting use speed not mining speed).
There are currently 14 different pickaxes available in Spirit, 7 of which are Hardmode-exclusive.