Both are good units. The FSP Aurum has the extra bling with a 80+ gold rating whereas the Xigmatek unit features an extra 100W of power. So if you do not need more than 600W for your system then surely get the FSP unit.
honestly i'm leaning towards the FSP one since i know it was a good brand. but i do not know much about Xigmatek. the Xigmatek one is modular and cheaper than FSP. but since i do not know much about it's quality i'm having difficulty on which one to pick