Here's part of the standard retail description for the HTC Titan:
The HTC TITAN is part of the range of new HTC Windows Phone Mango phones. Running on Windows Phone 7.5, the TITAN has the largest display of any Windows Phone handset. Measuring 4.7" across, the Super-LCD touch screen of the Titan is housed in a stylish unibody design and features a 480 x 800 resolution.
As well as its large capacitive touch screen, the TITAN has a super-slim profile - measuring just 9.9mm in thickness. Its contoured design adds to its aesthetic appeal, while the newest version of Windows Phone makes multi-tasking better than ever on the Microsoft platform.
and here's the description for the HTC Radar:
The HTC Rader is a phone which makes managing your life easy. All of your contacts and their social media threads are held within the HTC HUB making it easy to find out what is happening. It is also easier than ever to tag your photos and upload them to Facebook to share. The 5 megapixel camera is able to capture great photos due to its f 2/2 aperture, LED flash and BSI sensors. Best of all the body of the HTC Radar is constructed from a single piece of polished metal. This ensures that you instantly make a statement.
Featuring Windows Phone 7.5 you benefit from hundreds of improvements and updates. These include integrated search functionality, local scout and convenient access to a skydrive. Windows Explorer 9 is supplied with the browsing experience significantly improved as a result.