What is a good metal double bass pedal?

real personal thing for each drummer individually but here are my points on that.

Almost every drummer cranks springs on their pedals so that's the major factor in playing fast double bass.Just from the physics standpoint it's easier to hit the surface when the rebound from spring is there. Also your technique(lifting whole leg/playing using only ankles or combination of both), basshead tension(looser gives more lowend while reducing the response of your pedals/tighter obviously produces more rebound even with loose springs but also makes your bassdrum sound much higher and longer though this could be solved with few towels) and sitting position or your throne height affect the speed, power and thus the feel and settings of your pedal. Other bits include beater height and angle: in order to play loud you should put beaters relatively high and have them angled at 45 degree angle. From that point as you'll be playing you can twitch them up or down by your preferance. By the time your playing skills will improve, you'll figure out specific adjustments that'll be comfy.