What type of harmonizer should I get?

I have a line 6 spider lV 75 it has a smart harmony feature on it, I dont know exactly how to use it but I can tell its garbage. So I need help finding a good non expensive pedal. Ive been looking at the boss ps-6 harmonist it seems pretty good. Im trying to find a good one so I can do 2 guitar harmonies like orion, to live is to die, or fight fire with fire by metallica also like the main riff to hanger 18 by megadeth. I have watched acouple of vids on youtube but I dont know how well it will work. Could somone please help me that has used the boss ps-6 or someone who knows what would work better