Yeah ESP, as I understand will use a mix of power to the front wheels (unless 4WD) and brakes all round to stabilise the car, so if you have understeer it will slow down the appropriate corner to control it, it will also apply brakes to counteract the back end stepping out.... it goes on, youtube has some good examples of the system. TCS however just prevents wheel spin on the drive wheels and cuts the power till it gets grip and gives you the car back.
Both are great systems, yes sometimes the TCS can be a bit eager. But the ESP definately saves lives.
ED