Insurance does work in Argentina, if you go with a large, reputable company, and if you have the patience to go to court if necessary. My husband got rear-ended twice, and yes, both times the insurance companies were reluctant to pay out, but after taking them to court and being patient he ended up getting even more money than he had asked simply because the Judge lost patience with the insurance company and told them if they hadn't been jerks and delayed the process so long he would have had them pay the minimum that my husband had asked, but since they had wasted the court's time, he ordered them to pay 3x what we were asking.
It's worth having the insurance, if something happens, it is never as straight-forward as filing a claim and waiting for compensation, but if you go with a reputable company you will eventually get a pay out -- and usually it is best not to accept the first offer, you have to hold out.