So what are the advantages and disadvantages of different smartphone sizes? Like I mentioned in the previous post, a bigger smartphone is better for interaction but limits one handed use. So what else play a role in this comparison?
The biggest issue with the current generation smartphones is the battery life. And better the ability of the phone to keep its user engaged, more the drain on the battery life. So a bigger iPhone for example means there is more room for a physically bigger battery. And this seems to be the only thing that can improve the battery life of lithium ion batteries (come on Li ion battery industry, wake up and show us some innovation...). Of course bigger screen means more displays to push and this means more battery consumption that the smaller phone, but so far it looks like the gain in the battery size is still greater than the drain due to more pixels. This is what phones like Droid Max came in such a bulky package and claimed to give days of battery life. And from Apple's keynote on the iPhone 6 it is clear that, that is exactly what you get with the bigger iPhone 6, that shows significant battery life gain!
Ideally as a consumer I would want an iPhone is multiple sizes with exact same internals to make my decision easier. Or in other words I should not be forced to choose between say a more compact iPhone and a slower or less powerful one. While this looks on the surface to be customer friendly, is it really? A bigger iPhone for example can house a bigger battery and if there is going to extra space created because of a bigger screen, it is only wise to take advantage of that extra space by housing a bigger battery. Also the iPhone 6 Plus, thanks to its bigger frame, can house a whole physical optical image stabilization kit in its camera housing, while the iPhone 6 4.7" cannot. So again bigger frames results in better specs. We have seen the same with the MacBooks, the MacBook Airs that are super thin and portable have the least powerful processors, while the MacBook Pro 13" comes in second with the 15" MacBook pros have industry leading performance. Hence bigger technology products are bound to have better performance (not portability). So Apple forcing us to choose between a more compact but "weaker" specced iPhone 6 and a "bulky" but super specced iPhone 6 Plus, is only logical!
Apple's product model strategy
Finally any astute Apple watcher knows a couple of things. One that Apple doesn't flood its product offerings with a bunch of different models (different designs in particular) of the same device at the same, that too not during the first few generations of a new product. The iPod came in one size and design (albeit with different memory capacities), the iMac, the MacBook (or the PowerBook), etc all came in just one design initially. Once the products matures and the markets materialize, Apple diversified its offerings to suit a bigger range of its consumer needs, like portability loving MacBook Air owners to extreme performance mongers of the MacBook Pros. This is quite common across multiple consumer technology companies, though some are more smarter than the others when it comes to implementation. So as far as Apple is concerned for the iPhone which is a little more than seven years old now, to diversify, is only natural. It can be argued that Apple should have done this a while back, but they did do it, not the way you and I wanted, but in their own way, by offering their older generation iPhone models at a lower cost.
So if Apple was criticized for not giving its iPhone users enough choice before, now with the standard latest generation of the iPhone being the iPhone 6 that comes in 4.7" size, Apple is being criticized for making the iPhone too big! If you want a compact (depends how you define compact) iPhone then you are stuck with the iPhone 5C or the iPhone 5S both of which are one generation old. So what should Apple do? Do the same thing they did with the iPhone 5C? Keep the older generation iPhone but brand it differently? Could be... After all that is what computer manufacturers do, even Apple for that matter. Have you noticed that the 15" MacBook Pro gets Intel's latest and the greatest processor first and then it gets handed down (sort of with some minor modifications/improvements) to the 13" Pros a year later? When this is done with the iPhone, it is suddenly an outrageous crime?
In summary the ultimate choice between the iPhone 6 and 6 Plus boils down which do you need the most, portability or power (here power also comes at the cost of more dollars), you cannot have your cake and eat it too!