I personally think that The Weeknd looks better with his hair cut short, but that is just my opinion. His short hair is definitely more mainstream and some may see this as an example of his selling out to a more mainstream culture.
The Weeknd's old hair style was more radical and some may have seen as more genuine. With either hair style I think he looks good, but I would prefer to see him stay with the more conservative short hairstyle that he has now.