The Good: Absolutely brimming with power, the Sony Xperia X Performance is well designed and the only new Xperia to be waterproof. The Bad: Battery life needs a big boost for this phone to live up to its potential. The Bottom Line: The Xperia X Performance runs rings around the basic Xperia X and is a great phone for anyone who likes their handsets with a bit of grunt. If you're a "Top Gun" type and expect your phone to have the power of a jet engine, then you're exactly who Sony had in mind with the Xperia X Performance.The X Performance (never to be called the XP, I'm told by Sony) is the turbo-charged version of the . Sony has packed more processing power into the Performance, along with speedier LTE 4G connectivity and a slightly bigger battery. Other than that, the two phones are almost identical, from the 5-inch full HD screen to the 23-megapixel camera on the rear. But trust me, the differences are very noticeable. At $699 or AU$999, it's less expensive than I'd anticipated. (There are no pricing or launch details for the UK, but the price converts to around \u00a3525.) With the basic X model costing $549, AU$799 or \u00a3450, that's not much of a price hike at all.DesignWhen I first saw the phone, I confess to finding the smooth, rounded edges and matte back a little pedestrian. But my opinion changed significantly while using it. It's comfortable to hold, and when I went back to compare it with the and I found it to be the best looker of the group. My colleague Jessica Dolcourt called the Xperia X a "great one-handed phone" and the same goes for the Performance. Where she and I disagree is on screen size: A 5-inch screen is perfect for her dainty fingers. My hands are about twice as big, and 5-inch phones make me feel like I'm using a Fisher Price "My First Phone" toy. But 5-inches is what's on offer here and I happily admit that's a good size for 80 percent of the world.PerformanceWith the word Performance in the name, I had some high expectations for this phone and it didn't disappoint. The Qualcomm Snapdragon 820 quad-core 64-bit processor is a big jump up from the X and the numbers prove it. It far outstrips the Xperia X and actually rivals the .The phone feels exceptionally slick and fast. Apps open rapidly and navigating is smooth as silk. This speed even transfers over to the fingerprint sensor. Built into the power button like previous Xperia models, this is the most reliable and quick biometric security I've ever used on a phone. If you're in the US, however, you'll just have to take my word for it, because Sony has disabled the fingerprint scanner for your region.