What cam should I get?

OK....today I talked to Bob who built the motor. He said that it has a mild Crane cam in it and could not remember the specs since it has been a while. But he does remember that he installed performance type valve springs that he said would handle a larger lift cam than the one that is in it. Also he said the motor is bored .60 over and has 10:1 compression with forged pistons. It has a brand new crank since he said the stock one was bad. I asked him that I wanted to install a bigger cam that had a good lope to it and what would he sugguest and he told me Comp Cam Magnum series. And not to go over 280 duration. Now my question is Magnum series or Xtreme energy cam? What is the main difference? I'm going to check out Comp Cam's web site to see but I wanted to just know what you guys think?