iPhone 4S: Which is the best carrier?

The recently announced iPhone 4S will be available not just for AT&T and Verizon, but also for Sprint. This means that for the first time, an iPhone will be available on three of the four major U.S. carriers.

The iPhone 4S has a few notable improvements over the iPhone 4, including a faster dual-core A5 chip and an 8-megapixel camera capable of 1080p HD video capture. If you're a Sprint customer, you might be happy that you have an iPhone at all, 4S or not.

The iPhone 4S will have the same hardware across all three carriers--the same processor, same camera, and same dual-mode CDMA/GSM chipset, even if that chipset isn't activated for all carriers (see AT&T section below). We're also still watching to see how the world chip plays out in terms of global cellular coverage, if Sprint and Verizon will unlock the GSM portion of the chipset so you can easily slide in a GSM SIM card when you travel abroad (GSM will not work on Verizon and Sprint in the U.S.).

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Now, just because it's got the same innards doesn't mean you'll get the same experience across the board. Carrier coverage fluctuates from region to region--AT&T might have poor performance in San Francisco, but great signal strength elsewhere. Data plans are different for each carrier, too, as are customer service and the terms of your early-termination fees. Also, keep in mind that even though Sprint and Verizon both operate on CDMA networks, if you buy an iPhone 4S for one carrier, you won't be able to swap it to another, so if you pick Sprint or Verizon, you're stuck unless you want to buy your device anew. So choose wisely.

We'll perform a deeper test of the iPhone 4S in the weeks following the launch, but in the meantime we've put together a guide that might help you decide which carrier to go with if you're in the market for the new iPhone 4S.

iPhone 4S data plans

AT&T iPhone 4S

Pros: Even though the iPhone 4S has a dual-mode CDMA/GSM chipset, AT&T only activates the GSM technology if you subscribe with AT&T (so you won't be able to swap over to a CDMA network like Verizon or Sprint). AT&T's GSM technology gives you a speed advantage, though, since AT&T's HSPA+ 14.4Mbps data network is theoretically much faster than Verizon's and Sprint's EV-DO Rev. A, which have a theoretical maximum of only 3.2Mbps. Additionally, it offers simultaneous voice and data, which the others lack.

Cons: AT&T is notorious for dropped calls, and a fast data network is of no use if you don't have access to it, depending on where you live.

In sum: If you're a multitasking speed hound who needs simultaneous voice and data, AT&T is your only option.

Verizon iPhone 4S

Pros: Verizon is known for broad and reliable nationwide coverage and steady customer service. With the iPhone 4, Verizon became the second carrier to get an iPhone, so it's proven that the network can handle both the additional iPhone 4S traffic and your customer service needs. The iPhone 4S's dual GSM/CDMA chip makes it a world phone.

Cons: Verizon's investment in 4G LTE surpasses the other U.S. carriers; the non-4G iPhone 4S is going to pale in comparison with rival Android phones that can tap into Verizon's zippy 4G speeds. (See CNET's iPhone 4 speed tests.) As it's a CDMA phone, you can't talk and use data at the same time.

In sum: With its proven network strength and coverage, Verizon may be the safest choice for Apple fans who haven't yet taken the plunge, but only those who don't place a premium on having the fastest data speeds money can buy.

Sprint iPhone 4S

Pros: Sprint has promised unlimited data for the iPhone 4S, unlike AT&T and Verizon, which are tiered. That makes Sprint potentially the most affordable iPhone 4S provider when it comes to the most data-intense users streaming videos, downloading music, and playing online games from their devices. The iPhone 4S' dual GSM/CDMA chip makes it a world phone.

Cons: Sprint has never carried the iPhone in any form. Despite assurances that its network can shoulder the onslaught of iPhone traffic, the claim remains untested. There's the chance that Sprint could drop coverage or throttle speeds. As it's a CDMA phone, you can't talk and use data at the same time.

In sum: As the nation's third-largest carrier, Sprint has the most to gain from adding the iPhone to its lineup, and if Sprint can pull it off, that unlimited data plan is hard for heavy users to beat. After all, the lack of an iPhone was customers' top reason for leaving the carrier. On the other hand, Sprint's data ambition also makes it the riskiest iPhone 4S carrier choice, and Sprint will suffer more defections and derision should its network promises fail.

A word on Sprint
Sprint's pricing structure is a little different from those of AT&T and Verizon, since the unlimited option bundles data into voice plans for individuals and families. The lowest all-inclusive price starts at $69 a month for individuals, plus a $10 data supplement, and includes 450 peak minutes. The priciest plan for single users is a $110 monthly rate, and it includes just about everything (even the $10 monthly data supplement).

You'll need to consider these prices as well when you shop for your iPhone 4S, as you would when you shop for a rate plan on AT&T and Verizon as well.

Editors' note: Although it is not listed in the above chart, a $10 data supplement also applies to family plans.

Article updated Friday at 9:08 a.m. PT and at 1:23 p.m. PT with more details.