I find wax to be more effective on rougher surfaced papers.
Once wax is on the painting, it does not come off and the area will resist paint forever.
Always make certain you want the wax to stay on the paper. Be careful where you apply wax to your painting. It cannot be completely removed with an iron and newsprint. Some always remains behind. Also, just using masking changes the surface of the paper. Wax resists gouache too. You can't just touch up your mistakes! If you're not sure, use masking. Masking is removable, wax is not.
Using wax somewhere you change your mind!