The unlocked version of the iPhone 6s ($649; 16GB) takes the doubt away from potential Apple phone buyers who want to be able to freely switch between carriers. With excellent speeds and reception on all four major U.S. networks, as well as superior performance abroad, the unlocked iPhone 6s delivers a significantly better Internet experience than any previous iPhone. And that's not even getting to its top-notch cameras, faster processor, or the potential inherent in Apple's new 3D Touch feature. That makes the iPhone 6s our Editors' Choice for unlocked smartphones.

Going Unlocked
Read our original iPhone 6s review for general details about the phone. Here, we'll talk about features specific to the unlocked model.

There are two iPhone 6s models available from Apple. The A1687 model, which is sold by Sprint, T-Mobile, and Verizon, works very well on all three of those networks, and pretty well on AT&T, but lacks the brand-new Band 30 that AT&T is using to backstop LTE speeds in dense cities. The unlocked iPhone 6s is the same as the AT&T model, A1633, which includes all of the bands on the A1687 model, plus AT&T's Band 30.

The iPhone 6s has significant cellular radio improvements for three of the four major U.S. carriers. On Sprint, we found that iPhone 6s speeds are 50 percent faster than iPhone 6 speeds, because the phone now supports carrier aggregation, which bonds lanes of spectrum together to make a wider road for your data. On T-Mobile, the presence of Band 12 gives the carrier better building penetration and reach into suburban and exurban areas. On AT&T, Band 30 will speed up performance in some congested cities. There's no special new band for Verizon, but the phone's ability to more quickly recover from dead zones will make the phone feel sprightly there.

 See How We Test Cell Phones

Comparisons and Conclusions
There are relatively few phones that can operate freely on all four U.S. carriers, plus most international carriers. The iPhone 6 series, the iPhone 6s lineup, the Moto X Pure Edition, and Google's Nexus phones are the only ones we know of. The Samsung Galaxy S6 is an excellent Android phone close to the iPhone 6s in size, but it's not legitimately sold unlocked in the U.S.

This is a powerful set of competitors, but the iPhone 6s has a key advantage: Size. The Moto X Pure Edition and the Nexus 6P are both very large phablets, which a lot of people like, but which don't fit into smaller hands or smaller pockets nearly as well as the iPhone 6s. The Nexus 5X is certainly more affordable than the iPhone, and it has a great camera, but it's still bulkier and just doesn't feel as premium all around. Then there's Apple's unbeatable third-party apps and its excellent service and support through its network of stores to consider. 

We're comfortable naming both the Apple iPhone 6s and the Google Nexus 6P as Editors' Choice for unlocked smartphones, because the form factors are so different. The Nexus is a huge window onto a rich, flexible Internet world. The iPhone 6s is a pocketable personal computer with extremely high-quality apps, games, and support.