Need help choosing between 2 HDD by WD

Hi guys

I have 2 hdd's lying around that i want to add to my rig for data storage

Speed is more relevant to me than capacity

These are the options;
WD5000AAKX (500gb wd caviar blue)
WD1002FAEX-00Z3A0 (1tb black)

i have tried to find some info online but it was not that clear to me, so if you guys can clarify this one for me, would be great