I actually disagree with you completely. (And I'm a professional, this is my day job.) For breadboarding I buy from Adafruit and Sparkfun, since they have good selections of breakout boards, MSOP to DIP adapters, etc. DK and Mouser have plenty of that, and some really nice stuff (like TI's adapter "EVMs")... but for prototyping on a breadboard, I start with the other guys.

(Then usually tack them on to a Digi-Key or Mouser order, because if it doesn't require something weird, I probably didn't need to prototype it.)