At the super low levels you might - might - be able to feel the difference between the "best" and "worst" races for a specific class. The stat range from best to worst for a main combat stat(regardless of class) runs about 5 points. Thats roughly equal to the stat boost you would get from a level 20 character wearing a shirt vs no shirt. That isnt nothing, but its still basically meaningless. By the time you get to level 50 the stat boost from just a shirt is more then 10 times that initial spread from best to worst was, and thats not even close to the current endgame situation(the "starter" level 80 shirt has more then 400 main stat). So yeah, you might feel the difference slightly early on, but over time those differences become utterly meaningless.