The 25 days of T-Mobile holiday special is kicking off today, and the un-carrier is starting the festivities by giving $50 off on your purchase of a HTC One M8 or HTC One M8 for Windows. This means you will be paying $535 for either the Android or Windows Phone variant of the HTC One instead of the usual $585
Both variants of the device feature the same internal hardware, but offer completely different software experiences.
On the hardware side you get a 5 inch Super LCD3 display with a 1080 by 1920 pixel resolution, 32GB of internal storage which can be expanded through microSD, twin 4 megapixel rear UltraPixel Duo cameras, a secondary 5MP font facing camera for video calls and a 2.3GHz quad-core Snapdragon 801 processor with 2GB of RAM.
On the software side, the Android variant offers Android 4.4 KitKat with the HTC Sense UI. An update to Lollipop expected soon. Meanwhile the Windows variant has Windows Phone 8.1, and will likely be updated to Windows 10 in 2015.
source - T-Mobile (Twitter)