IIRC the Dragon Ball creator pretty much said that power levels were mentioned to be pointless. To show they don't matter and that anyone could win really.
Obviously, a lot of people don't see it this way.
I like the way Dragon Ball handled it; we started with a few supernaturally powerful characters who were considerably stronger than the average human, to them basically becoming superhuman with a few magical powers, to them becoming something of unstoppable to all forms of technology with lots of magical-esk powers, to them being demi-Gods who can fly and do pretty much unlimited forms of superhuman powers. Everything power-level wise was a gradual things.
But no, in Dragon Ball Z, it went from "hey, we got vehicles that can drive as fast as you can fly" to "I can blow up the world without breaking a sweat" from one saga to the next.
Oh, and unlike Dragon Ball, the jump from the Saiyan to Namek saga was a mere month or two, instead of say a few year gap between the major sagas in Dragon Ball. But hey, at least the jump in power levels from then on made sense, as there were larger times gaps (although the insane power level boosts via the Hyperbolic Time Chamber in the Android Saga still was too big of a jump).