Those indicate the "displacement" (cc = cubic centimeters) of the engine, which in turn is a rough guide to power. The bigger the displacement, the more power the engine will make (given the same engine design).
Given your question, you should be starting out on a very small engine. 250 cc is plenty for a beginner bike, and it can be adequate even for an expert.
(i know you said "Same engine design" but I'm not sure if he will understand...)
When considering power you also have to consider a number of other things. The number of cylinders matters greatly to the power, power delivery and feel of the engine. A kawasaki Ninja ZX-6(600cc four cylinder) is alot more powerful than a Ninja 650 (650cc two cylinder.) The 650 is alot more appropriate for a first bike, though Sachi is right a 250 or possible a 500 twin would be a better choice.