I've heard (on this forum) that the PZEV tank is metal, but I have not seen that on the Hyundai site. But if I had a choice, I'd say metal anyway. I think it's 3 HP lower and has an extended emissions warranty. There were 6 states in the original green state group, CA and OR both in, and more states participating now. I didn't have a choice and I am fine with PZEV.
Had a 2011 PZEV Limited sedan. My 2013 is non-PZEV. I honestly can not tell one iota's worth of difference in performance. I thought there was 1 less HP with the PZEV. Maybe it was 1 less foot pound of torque. For me? Who cares! That's like having one less ant in an army of ants carrying food back to the queen. The food still arrives.
Two major differences are the metal gas tank and the full metal gas filler tube. The rest is emissions fluff, I believe. If you have one, you're good. If you DON'T have one, you're good too!
PZEV vehicles have much longer warranties for emissions-related components - 15 years/150K miles. However, this extra warranty may only apply if the car was sold in CA. The language in the warranty booklet says this extension applies to "2013 Hyundai SULEV and PZEV vehicles certified for sale in California" What happens if you have a PZEV vehicle which meets requirements for sale in CA that is sold in another state? Or if you buy a used PZEV car originally sold in CA but now living in another state? I don't know.
I'm not aware of any specific concerns about problems with PZEV vehicles. The only drawback I see is that power is down 3-hp.