The true answer might depend what industry you are looking into.
Aerospace and Automotive may have preferences for one CAD system, while Consumer Products prefer something different, and Machinary or Mold Design somethign else.
A different CAD program might be more suitable for creating free-flowing swoopy surfaces as compared to welding together structural tubing.
Similar to what Drawoh said, if you are very good with one CAD package, transitioning to another shouldn't be very difficult. They all perform essentially the same functions, it's just a slightly different language.
If I had to pick any CAD program to excel at, it would be SolidWorks. But I'm proabably biased, as are most people in this SW forum.