First of all, if both of your compressors are running load & unload frequently at the same time, then there is something wrong with your compressor pressure setting. Most likely both compressors are having similar pressure setting, which is not advisable.
During unloading, compressor still consume about 30% motor power. Also, the transient period from loading to unloading, the compressor consume more than 30% power. These are wasted energy, not producing any air.
You should set the bigger compressor (the 100hp) to higher unloading point than the smaller compressor. This will let the bigger unit to run a full load, without any unloading. With this, the 100hp will be running at its better efficiency point (full load).
Try this. You will see the energy saving by doing this simple adjustment.