The AWR endlinks are stronger. I know that I pretty much destroyed the stock endlinks getting my stock sway off.
Also (if the 19mm is set up the same as the 21.5mm) the endlinks can be adjusted so that you can set up the stiffness of the bar. I don't use it that much, but occasionally on a nice day I'll stiffen it up and see if I can get the car to oversteer.