Not sure as most of Charles' actual prime isn't filmed. From what is on film however, it's clearly Ali imo; and I've seen comparisons between Ali and Robinson's jab where Ali's was quicker. That's crazy hand speed for any weight, let alone a proper heavyweight. P4P its 100% Ali and in actual terms it's probably Ali as well.
I think it's evident that Ali is clearly faster than Charles on tape. Charles is a much more technically correct puncher but speed, I don't think it's close enough to be genuinely debatable. As @George Crowcroft said earlier, Ali's jab is measured as faster than SRR's and then when you factor moving around and a longer reach/distance to target, the speed is speeding expeditiously.
Relative to peak Ali: 1. On a P4P basis vs any version of Charles = Ali is my guess 2. In absolute terms vs the Charles most have seen clear footage of from his HW contests = Ali 3. In absolute terms vs a peak LHW Charles = uncertain because of the lack of quality footage, but my guess is Charles. Here he is vs Lloyd Marshall, the quality isn't great, but you get a feel his hands were faster than when he was up at HW - This content is protected
Shiiiit Somehow I misread the title as Chambers vs Ali and snickered, voted, then realized my mistake.