Lol, if you have a bag of purple weed, yes it looks pretty, but thats it. There are very few strains out there that are actually "purple". Most of the time it is because the plants are stressed with lower temps during the flower period, dropping temps to between 40-50 degrees. Or its likely from the plants having a phosphate defficiancy, which will also impart a purple color to the plants, usually starting with the stems. If you do get a strain that is genetically purple, you still may not get purple plants, it depends on what phenotype of that strain you end up getting!!
Purple weed is only for bag appeal, it isn't stronger, and depending on how it is "made" purple, it may actually have less resin production, due to the stress, and lower temps which also slow growth, and starving a plant of phosphate is just dumb!! If you want killer weed, then grow killer weed! If you want purple, then you need to do serious research on the strain you are gonna grow, and find one that has purple phenotypes, and cross your fingers. Any other way is counter productive!
(spits water everywhere)