I know different WUs take different amounts of time

even if the point values are the same, time to complete can vary
between my 2GHz P4 and my A64 3700 (at stock 2.2GHz speed) the A64 is about double the speed on the same WU, and when my A64 is clocked to 2.6GHz it is about 20-25% faster than stock on the same WU