It's that time of year again when the Apple marketing machine tries to convince millions of people that their once shiny new iPhone is now ready for the scrap heap. The iPhone 5 is an impressive upgrade in many ways, but it's not as breathtaking as the leap from the iPhone 3G/S to the 4. Plenty of people will hand over their money regardless, but some iPhone 4/S owners could be a little underwhelmed by the iPhone 5.

There's a lot to like about the iPhone 5, but after spending time with review units from Vodafone and Optus I wouldn't necessarily say bigger is better when it comes to the 4-inch screen. This isn't a full iPhone 5 review, as there are plenty of them around, this is just a closer look at one interesting aspect of the iPhone 5. The fact that the phone is thinner and lighter is more likely to grab your immediate attention. But a taller screen doesn't actually bring that much to the party when it's no wider.

The beauty of the 4.7 and 4.8-inch displays on the Android superphones is not just that they let you see more, but that they're wider so everything can be that bit bigger. You don't get that advantage with the iPhone 5, unless you're in the habit of turning your iPhone on the side -- which you're unlikely to do when checking your email or browsing the web.

When you hold the iPhone 5 upright in portrait mode everything looks exactly the same as the iPhone 4/S, the only benefit is that you can see an extra centimetre or so at the bottom. So you won't need to scroll as much, but otherwise you won't really get the usability benefits that you'd hope for from a larger display. Don't expect to be as impressed as you were when the iPhone 4 made the impressive leap to the sharper retina display.

It's not just me, all the current iPhone owners who've handled my iPhone 5 review unit were underwhelmed by the larger screen. They were expecting the extra screen real estate to slap you in the face, like a Samsung Galaxy S III, but it doesn't. In day to day use you'd barely notice the iPhone 5's taller screen. You're more likely to notice the expense of buying new accessories to cope with the new screen size (not to mention the new connector).

The iPhone 5's extra screen real estate pays off when you turn the phone on its side to watch a movie. The widescreen movie format fits almost perfectly with the iPhone 5's wider display, with only the slightest of letterboxing at the top and bottom which you'd barely notice. On an old iPhone 4/4S you're faced with significant letterboxing when watching a movie, unless you want to zoom in and lose the edges of the picture.

Watching movies on the iPhone 5 also shows off the fact that Apple has improved the screen quality. Whites are whiter and brighter, improving the contrast, while colours are more vivid. Dark scenes in movies such as Men in Black III look considerably better. The iPhone 4 already had one of the best screens of any handheld gadget when it came to image quality, putting the overblown AMOLED screens on early Android devices to shame. Yet the iPhone 5 manages to improve on it again. If anything I'd say the iPhone 5's whites are a tad too warm for my liking compared to the iPhone 4, but not enough to complain about.

It will be interesting to see what app developers do to take advantage of that extra screen real estate, such as Firemonkeys' upcoming Real Racing 3. For now iOS5 apps are slightly letterboxed on the iPhone 5 but it's not enough to be annoying, especially on a black iPhone where the letterboxing just fades into the bezel.

Unfortunately the iPhone 5 seems to have inherited the iPhone 4S' issues with the angle of the anti-glare polarisation. When I look at the iPhone 5 wearing my polarised sunglasses the colours are off unless I turn it on an angle. The 4S is the same, whereas the iPhone 4 looks fine in portrait mode unless you turn it slightly. It's rather annoying but not a deal-breaker.

Personally I don't think iPhone owners were crying out for a bigger screen. If the iPhone 5 had stuck with 3.5 inches, the fanboys would still be telling us it's the perfect size for a smartphone. But Apple obviously felt the pressure from the Android superphones and needed to respond.

I think Apple should have either left the screen as it was or made it both taller and wider to deliver real usability benefits. On the other hand, I can appreciate that retaining the same width helps limit fragmentation of the iOS platform. But this half-hearted approach to the larger screen is likely to leave many iPhone owners underwhelmed, yet still requiring a new set of accessories. If Apple offered an iPhone 5 model which retained the iPhone 4's 3.5-inch screen size and old connector, but offered all the other benefits, I'd jump at that model over a 4-inch iPhone 5.

Of course there's far more to the iPhone 5 than a larger screen and I'll take a closer look at some the phone's other new features, such as the improved camera, later in the week.