How important is screen real estate when choosing a smartphone?

I've been playing with a lot of Android phones recently, along with the new iPhone 4. While Apple takes a one-size-fits-all approach to its wunderphone, Android phones come in all shapes and sizes. I still think the best tend to be those which mimic the iPhone.

If you want a decent onscreen keyboard, I think you need to draw the line at 3.5-inches. Anything smaller and the onscreen keyboard is just too cumbersome to type on. Even half an inch makes a huge difference - you really feel the difference switching between the 3.7-inch display on the HTC Desire and the 3.2-inch display on the HTC Legend. If you are tempted by an Android phone with a sub-3.5-inch display, take a look at the Swype keyboard app which lets you drag your finger between letters rather than pecking away. It makes a big difference when using a small phone. Swype is also on the Samsung Galaxy S (pictured), not that it needs it with that generous 4-inch display,

Along with screen size, you also need to think about screen resolution. When Android was first released, the standard screen resolution was 480x320 and applications were developed to suit this resolution. While the screen resolution has risen on the high-end Android phones, it's also dropped to 320x240 on some of the small Android phones - such as the Sony Ericsson Xperia X10 Mini Pro and the new HTC Wildfire. The problem is that some Android apps won't run on these phones, as it requires the developer to specifically design the app with 320x240 resolution in mind. I couldn't say exactly how many apps you're missing out on, but you'd want to do some research on your favourite apps (particularly games) before buying a 320x240 Android phone.

Screen technology is also a factor to consider. Older Android phones used a TFT display, while high-end Android phones tend to use an AMOLED display (like the HTC Desire) or a Super AMOLED display (like the Samsung Galaxy S). HTC is looking to switch to the IPS "Super" LCD displays, as used on the iPhone 4.

Your choice of screen technology impacts on your battery life and how the phone handles outdoor glare. The Galaxy S' Super AMOLED display handles outdoor glare better than the AMOLED display on the HTC Desire, but not as well as the IPS LCD display on the iPhone 4. AMOLED displays also chew through your battery faster than Super AMOLED, although the trade off with the Galaxy S is that whites have a very distinct blue tinge. The whites are whiter on the Desire and even whiter again on the iPhone 4. TFT displays still have their place - offering excellent battery life and outdoor performance on Motorola's Android-powered Quench.

Phones with a "capacitive" touchscreen display respond far better to your touch than those with a "resistive" touchscreen display. The resistive display on the Android-powered LG Optimus is one of the main reasons why it's so horrible to use compared to other Android phones.

What are your preferences when it comes to smartphone screens?