In the video department, the Leica X2 has to be kept aside as it does not come with the video recording feature. The new Leica X-U is capable of shooting full HD videos at 30 fps. It even comes with an option of shooting videos in 1280 x 720px resolutions. The Leica X Vario on the other hand comes with the capability of recording full HD videos at 1920 x 1080px resolution.
The Leica X-U is the hands down winner when it comes to the durability of the devices. It is built to be shock, water and dust resistant and is perfect for people who has a knack for adventure sports. Its siblings fall way short in this department as they are not built for durability and thus they may not be the perfect choice for photography under unfavorable conditions.
Overall, it can be stated that all the cameras share similar features and are also unique in their own ways. The X-U no doubt would be the first choice in case of outdoor photography. The X2 is more suited for casual usage and the Vario will likely be the first preference when it comes to professional photography.
Stay tuned for more update on Leica X-U.