Of course it's how you use it. But even in your case, you're likely paying a LOT for that 10GB plan and that won't be a typical plan for the average user. Even paying the Apple on-board storage premium for getting more on-board storage than the 16GB he was advocating would probably save money for most. Sync instead of stream and have all that media you want to play when away from wifi. iCloud would still be accessible if you wanted something you didn't sync but that would be a fall-back option instead of a primary.
Then, you might get a cheaper data plan because you'll use less cellular data and end up saving more money- perhaps much more money- than paying for data and buying a small (on board) memory iDevice. To go from 16GB on board to 64GB or 128GB is about $100 times 2 or 3 at Apple prices. $300/<monthly savings by dropping to a smaller data plan> should yield a relatively small number of months before the "sync more" option makes more sense (financially). Would this work for everyone? No, there's always the guy who's company or parents is paying for their plan but where someone has to pay for their own plan and aren't getting a unique deal not available to the masses, I would (very) generally suggest that "sync more" rather than "stream everything from the cloud" will prove to be better-to-much-better option for almost anyone who cares about not streaming more and more cash from their wallets.
