Current literature supports that Botox, Dysport, and Xeomin last about the same, kick in about the same, and have the same rare side effects. If you heard that one lasts longer, that is probably a myth started by someone who holds stock in one of the companies. They are all equally safe when injected properly.
It is possible, the prices will vary with variation in manufacturer's cost, and the products come in varying concentrations so one unit of Botox is not equivalent to one unit of Dysport.
Some patients develop a resistance to the effects of one of the products, so that may be a time to try a different Brand.
Zinc and Botox...
Recent literature supports that zinc is needed for Botox (Dysport, Xeomin) to function well in your skin. Considering many people may be zinc deficient, many cosmetic docs are advising their patients to try a zinc supplement for just a couple days before their treatment.
Don't overdo it with the zinc or you'll get diarrhea.
Take care in choosing your injector...
As a dermatologist, I am biased to seeing a dermatologist, or another aesthetic board-certified physician or their well-trained experienced P.A. or R.N. in the same office. Botox injection is not idiot-proof, for success it requires both an expert understanding of complex facial anatomy, which only medical professionals have, as well as an artistic edge which many aesthetic practitioners also have.