For users, the difference means that Dysport "spreads" more when injected, so it's more effective over larger areas like foreheads. As such, it's usually cheaper than Botox per treatment because it requires less product. On the other hand, Dysport's wider reach in muscle means that unless the person injecting really knows what he or she is doing, patients are more likely to get side effects like drooping eyelids from unintended muscle weakening. Uh-oh.
Injectables are one instance in which you really should consult with an experienced doctor, and with a new product like this one, it's doubly important to find someone who not only understands musculature but also has experience using the product. So if you're considering it, definitely ask your doctor how many patients she or he has treated with Dysport, and whether she or he has gone to a training seminar to use it.
Source: Flickr user adam.r stone