I'm not competive in PvP. I play with the characters I like, not based on who is good competitvely.
I advise you read the Blogs of Potkettleblack to get some insight on who you should use. No one can tell you who to use because they'll be at a different level to you and they will be facing different opponents to you. Thus, the only person who can tell you who to use is you. But PKB's Blogs are an excellent place to learn about the different methods you can use, and how to respond to what you are seeing in your opponents.
In the end, it's all down to trial and error. Try a team, and if it doesn't work, change it. : )