I hope someone more familiar with anarcho-syndicalism can address the particulars of this.
As I understand anarcho-syndicalism there are some distinct differences with anarcho-communism. Where as a-c is based on the idea of everything being communized and evenly distributed, a-s is based on workers at particular points of production working collectively and in collective effort with other workers at other points of production. I am not sure if the distinction is clear, which is why this is a comment.
Also, if you gave an anarcho-syndicalist and an anarcho-communist a knife and told them they had to fight it out for their ideology, they'd probably end up being friends and being executed by the cheka, but that is anecdotal.