There is no difference in the efficacy of hair removal in curly or straight hair. The way the laser works is the energy developed by the laser seeks the pigment in the "root" of the hair just beneath the skin.
The coarser the hair and the more pigment the more effective it seems to be.
In our office we ask patients to shave the day before treatment. You don't want to wax prior to laser hair removal, as there will be no hair left in the follicle to absorb the energy.