Still being slightly puzzled that a 12v impact driver could develop more torque than a 230v version, I decided on a practical trial. Hardly a major scientific experiment, I only did each trial once, but tried to keep things even
6mm x 90mm & 8mm x 100mm Turbogold coach screws into softwood, no pilot;
12v machine (135 Nm) did the 6mm in 4.06 secs, 8mm in 6.24 secs.
230v machine (100 Nm) did the 6mm in 7.15 secs, 8mm in 9.47 secs.
So the mains machine is actually slower in practice. Not enough to worry about, 7 seconds to drive in a 6mm coach bolt is hardly slow. The point in buying the mains machine was to reduce the load on the battery machine.
John Rumm's learned explanation "Well if you assume that the mechanical power out is approx half the electrical power in - that gives you 150W ish for the mains one, whereas the cordless will probably develop in excess of
200W". Seems spot on - but it didn't feel right.