Even though I agree with Sensation on most parts. I am of opinion that ping does play a major part in PvP. It is true that it has more impact on some classes than others. The class you'll notice ping difference most on is champion. Champion is one of the very few classes that benefit from low ping because they have low skill cooldowns and are all about speed. 150 ping is on the edge for champion. you won't be the fastest , you won't be the slowest either you'll just need to get used to the rhytm combined with your ping.
You should definitely be able to compete in pvp with 150 ping on pretty much every class :) Anything above that you'll notice a disadvantage on certain jobs. But in the end a lot comes down to player skill.