Processor

A phone’s processor is the brain of the device, and a fast one will enable you to open apps quickly, play games smoothly and even edit video. Today’s state-of-the-art chip for Android and Windows Phones is Qualcomm’s Snapdragon 800. (The 805 is coming soon.) This CPU offers swift multitasking and high-powered graphics in devices such as the Galaxy Note 3 and Lumia 1520.
The Snapdragon 600 (inside the HTC One) and S4 Pro (in the Moto X) are also very capable. On cheaper phones, you’ll find the Snapdragon 400 CPU, which offers fair performance for everyday tasks but isn’t designed for more intensive activities. For example, the Galaxy S4 Mini with this CPU took 7 minutes and 19 seconds to transcode a 1080p video clip, compared to just 5:15 for the Snapdragon 800-powered Galaxy Note 3.
For iOS, Apple’s A7 chip inside the iPhone 5s offers 64-bit power and about double the performance and graphics of its A6 CPU (in the iPhone 5c). That’s just one reason why you should invest in Apple’s higher-end device.
RAM
The amount of system memory plays a significant role in how well a smartphone performs. Today’s flagship devices offer 2GB to 3GB of RAM, while lower-end to midrange phones get away with 1 GB to 1.5 GB. If you want to load applications from memory faster and switch between them faster, more RAM is better.
Screen
The size of the screen definitely matters, but so do the brightness, sharpness, color and viewing angles. Right now, 1080p screens (1920 x 1080 pixels) are the sharpest you’ll find on smartphones. However, we’ve seen some 720p displays (1280 x 720 pixels), such as the one on the Moto X, deliver fantastic image quality. We highly recommend putting the smartphone in your hand to evaluate the viewing angles; if the screen washes out when you tilt the device, think twice about that purchase.
When testing smartphones, we hit every one with a light meter to get a lux rating, so be sure to read our reviews to find out how each handset stacks up. As far as screen technology, AMOLED panels (found on many Samsung phones) tend to produce very rich and saturated colors, while LCDs tend to offer more realistic hues. It really comes down to personal preference.
Storage and Expansion
Given that you’ll store everything from photos and music to videos and apps on your smartphone, opt for as much internal memory up front as you can. Although 16GB is fairly standard, we suggest 32GB of storage so you don’t run out of room. The 32GB iPhone 5s, for example, costs $299. But you’ll also find some cheaper options with that much space, such as the HTC One; it starts at $199 for 32GB.
It’s becoming a lot harder to find, but if you like the idea of expandable storage, choose a device that has a microSD card slot, such as the Samsung Galaxy S4, Note 3 and Mega.