pristiq vs effexor/brain fog

I'm deciding whether to go back on effexor or pristiq. Both gave me brain fog but there were some outlying circumstances that may have contributed to that. I remember going on pristiq and feeling blasted with brain fog after about two weeks but I don't remember if it eased up. I'm on cymbalta right now and feel like an absolute zombie. So yeah brain fog is my most feared factor in making the decision if anyone has anything to weigh in on this issue thanks in advance.