The FZ-E1 and FZ-X1 have similar looking hardware, but are actually quite different. The both have 5" screens (1280 x 720 resolution) and a rugged shell, but one runs Windows Embedded (Windows Phone) while the other runs Android 4.2.2 Jelly Bean.
The Windows-powered FZ-E1 runs on a 2.3GHz quad-core Qualcomm Snapdragon 800 processor, while the FZ-X1 uses a 1.7GHz quad-core Qualcomm Snapdragon 600 chip to run Android. Both models have 2GB RAM, 32GB Flash storage, and a couple cameras (1.3MP and 8MP). They also have LTE, WCDMA, EV-DO, and3G connectivity as well as Wifi and Bluetooth. In terms of battery life, the removable battery is rated for 6.2Ah, with Panasonic claiming 14 hours of continuous use or 1,000 hours of standby time.
Like all tablets in Panasonic's ToughPad range, these smartphones are designed to survive drops of up to 10 feet, and you can dunk them underwater to a depth of 1.5 meters for up to half an hour. And like their larger brethren, the FZ-E1 and FZ-X1 are designed to be bolted to other equipment using fixing screws.