Consumer Reports rates the new iPhone 6S and 6S Plus

NEW YORK (WABC) -- Apple says it sold more than 13 million iPhone 6S and 6S Plus phones in the three days since its iPhone launch.

But is the latest phone worth the upgrade? Consumer Reports reviewed the new models.

Photo experts tested the upgraded 12-megapixel camera and compared it to previous models. In their preliminary camera tests, they found the upgraded still camera is only slightly improved over the iPhone 6.

The test concluded that you probably won't notice the addition of four megapixels, but you may notice the larger file size on Apple's new "Live Photo" feature.

Consumer Reports says the files take up three times more space than just still photos, but the sizes may vary depending on your subject.

Camera testers found that the updated five-megapixel selfie camera has a wider-angle lens and works better in low light.

That's because the new retina flash uses the phone's screen to light up your face.

The screen is made of what Apple says is "the strongest cover glass used on any smartphone in the world."

To check if that makes it more scratch resistant, Consumer Reports put it through an abrasion test.

They found it was no better at resisting scratches than the iPhone 6.

"If you have an iPhone 4 or 5, you might consider upgrading to the 6S," Consumer Reports Glenn Derene said. "You'll appreciate the higher quality camera and some of the new features, but if you already have an iPhone 6, you won't see such a big difference and might want to save your money for the next version that Apple's bound to roll out next year."