Part of it is subjective, yes. But part of it is what works best for how people use the product. Screen size on a computer only really matters for one sense, our vision. Screen size on a touchscreen though starts to matter for two senses, touch and vision. Careful thought went into picking 3.5 inches, beyond just the vision aspect. This was an image someone made to point out one of the touch considerations. If you hold a phone in one hand, where can the average sized thumb touch?

I'm not saying Apple will never move away from 3.5 inches on the screen, nor am I saying 3.5 is absolutely perfect and everything else is wrong. Instead, I'm just trying to show some of the thought that goes into the decision. For Apple, they make one phone product, so they need to ponder the average user much more then a company like Samsung who releases many different phones every year. If Apple ships a fatally flawed product, they impact their business in a major way. If Samsung does the same, they simply bury it, burning just a few customers, and promote other phones more to make up for the mistake.


Part of it is likely the hardware, specifically in the resolution and quality of the touch screen digitizer. Android phones have been improving in this regard, but it's still hit or miss depending on the phone. The other part is software though. Apple has a huge advantage with there vertical integration. They can work as one company to optimize everything. From the silicon in the SOC design in the CPU (A4/A5) through the firmware for the touch screen, the OS, and the hardware. If it's something that has to be created, Apple will tend to do it, instead of compromising greatly. Apple engineered the machining process needed to build unibody laptops, and in turn the same process can be adapted to building the metal structure/antenna of the iPhone 4/4S.