Cheapest iPhone Comparison and tips for all tariffs including iPhone 4S

The new iPhone is certainly a step up from the current iPhone 4, but how different is it? We've taken a look at some of the new additions to feature on the device:

• iOS 5: The new operating system, iOS 5, includes several new features.
  
  Some of the best are iMessage, which is a BlackBerry Messenger-style app for iPhone, a Notification Bar which will display new notifications briefly at the top of your screen, without interrupting what you're doing (very much like the notification bar on Android mobiles), and Reminders which are "location aware", sending you a notification when you're near the supermarket, reminding you to pick up milk, for example.
  
  Anyone who already has an iPhone will be able to download the updated operating system for free, though we don't know yet whether they will be able to use all the new functionality.
• Improved graphics and processor: The iPhone 4S has the A5 dual-core processor from the iPad 2, which means it'll be slightly faster than the iPhone 4. The 4S also has dual-core graphics, which Apple claims are a 7x increase in the current model's graphic capability, and will mean a better experience for gamers.
• 8MP camera: The new 8MP camera is an improvement on the 5MP camera on the iPhone 4, and means the iPhone 4S will be capable of capturing video in 1080p HD. The original iPhone 4 can only manage 720p.
• Voice control function: The iPhone 4S will feature a voice control service, called "Siri". Users will be able to summon Siri by holding down the home button and asking it a question, eg, "Do I need a raincoat?". Siri will reply with a weather report, eg, "It sure looks like rain today."

There are quite a few differences between the iPhone 3GS and the iPhone 4, but here are the biggies:

• New look. The last two iPhones were basically identical; this one's made of toughened glass and stainless steel, and it's thinner than ever at 9.3mm.
• New screen. The iPhone 4 has an IPS screen which offers four times the resolution of the 3GS's - that is, it's 4x more detailed. But Apple head honcho Steve Jobs was at pains to point out when first showing the handset off, this makes it "higher res than the human eye."
• It's faster. Using Apple's A4 chip - the same as the iPad - the new iPhone's a fair bit faster than the previous version, and has double the RAM; 512MB compared to 256MB. That's twice the amount the iPad has too... This better places it to handle multiple apps at once, and it's supposed to be more power efficient too.
• Better camera. Previous generations of iPhone have always been lacking in the camera department. The new one's got a 5 megapixel camera with an LED flash built in; it's not revolutionary in itself, but it'll also be possible to get an iPhone version of the iMovie editing suite and edit together HD videos on your phone.
• FaceTime Video Calling. If your friends also have an iPhone 4, you'll be able to video call them over WiFi using the iPhone 4's front-facing camera. Of course, plenty of other phones have offered this capability in the past, they just didn't give it a silly name.
• Gyroscope. As well as the accelerometer sported by previous models, there's a 3-axis gyroscope which will undoubtedly be used by plenty of innovative games in the near future, and possibly some more useful apps like "augmented reality".

Always keen to be at the cutting edge of technology, Apple's cut the edges right off the standard Sim size, adopting a smaller, new micro-Sim (pictured right) for its iPhones and iPads, which for most is a bit annoying as it limits flexibility.

Only the size has changed though; the chip on the card remains exactly the same as before, which means those handy enough with a pair of scissors can cut their bigger Sim into the smaller size (as shown in TechRadar's guide) and still use it, at their own risk of course.

All networks now offer micro-Sims, but micro-Sim only deals are much thinner on the ground. Try micro-Sim deals from O2, Three Mobile and T-Mobile.

Smartphones are fast becoming the norm and if you use your phone to constantly search the web you need to watch the amount of data you use. As more data-hungry apps are released, it's fair to question whether you'll chomp through your data allowance quickly each month and wind up paying a wedge for more.

For checking emails, looking at Facebook and watching the odd YouTube video 500MB should be more than enough. To give you a rough idea, one of our techies, MSE Joe, has an iPhone 4 on Orange with a data allowance of 750MB/month. He doesn't use even half of this, averaging about 350MB of data a month using Spotify, Twitter, Facebook and email apps. He doesn't watch any videos however. Downloading videos, TV shows or other web heavy apps may take you over your limit and incur heavy charges.

If you're worried about data use, try using the free Onavo app mentioned below.

The vast majority of iPhone tariffs come with around 500MB of data a month. This is quite a lot, for example, Vodafone suggests 500MB will let you read and reply to approximately 100 emails, view 92 BBC news stories, and browse around 44 mobile web pages every day.

However, heavy downloaders who go over this could end up forking out loads in charges - especially if using your phone to surf the net while abroad (see the Data Roaming guide).

If that's you, try free iPhone app Onavo, which compresses data when web-browsing and using other apps such as Facebook and Twitter. This means that the same amount of surfing will only use a fraction of your data allowance, and avoid any hefty fees.

Onavo says it can reduce data usage by 80% (we've not been able to verify this yet, but please leave your feedback in the Onavo forum discussion) and is secure as it doesn't store any of your info. It works in 90 countries worldwide, so can help minimise expensive roaming rates too.

What does it do? It can compress data for the following, meaning you use less MB:

• General web browsing
• Many apps such as Facebook, Twitter
• Maps
• Downloading emails/email attachments.

What does it not do? There are a number of things Onavo cannot compress, crucially:

• Apps or internet sites that stream content (where you watch a video or listen to music directly via a website) such as BBC iPlayer or YouTube.
• VoIP apps, which you use to make calls via the internet, such Skype or Viber, and video calling services
• Downloading music, games or videos to buy.
• Uploading content, such as photos to Facebook.

How much does it cost? It's available free for iPhones at the moment, but Onavo says it will eventually start charging a subscription for new and existing users. This means you may have to cancel in future if you don't want to pay.

It depends to an extent where you are; across all the networks, big cities and towns should all have a decent 3G signal, while those in rural areas can struggle.

All the networks have coverage checkers on their sites, but these tend towards optimism. Ofcom's research into 3G at the beginning of 2009 still constitutes the most up-to-date objective info we have on coverage - view its network-by-network maps PDF.

Its conclusion put the networks in the following order overall based on outdoor coverage, though it's likely Orange now has top spot, following its merge with T-Mobile:

1st: Three
2nd: Orange
3rd: T-Mobile
4th: Vodafone
5th: O2