Career is what you come from. What your character develops into is your decision. WFRP Careers are no a min-maxer/powergamers wet dream (like in other generic systems like D&D or GURPS).
They are differentiated by roleplaying THEME, their skill set, and how good of a player you are. The other "abilities" are inconsequential, just as they were in previous editions of the game.
I've gamed with a lot of people over the years and if you handed some of these dorks two dwarf boatmen, other than by name, they wouldn't know how to think their way out of a paper bag regarding having an original personality, backstory, or going outside of "how to min-max" their skill at arms.
On the other hand, I've also gamed with a lot of people who are able to create an interesting character, without min-maxing stats, every time. These are the characters that you will remember YEARS after the game. They are characters who weren't measured by their damage per second or how many yellow dice they had in weapon skill.
Try not to look at their statistical aspects as the measure of a character. This game does a good job of making careers essentially equal..that forces players, like it or not, to have to do some thinking on their own during play on how to make the character live (or die) in interesting ways.