Neither. For around $20 you can get a new condition GI steel pot with camo cover. Why? Neither the old steel pot nor the newer ballistic/kevlar helmets will stop a rifle round, even at long range. Both will stop a 9mm. Save your money...the liklihood of you ever needing a helmet AND receiving a 5.56 round in the noggin at like 1,500m are astronomically low.
The marginal step up in performance coupled with the extremely low probability that that performance will be needed simply do not justify the HUGE increase in price.
I started a steel helmet collection, mostly inexpensive cold war stuff. There are some really cool designs, all are in new or excellent condition, and all were purchased for around $20. Ultimately, given the one in a million that I'll need a helmet, I have extras for the family.