Both of the phones will run on AT&T new 4G LTE and the HSPA+ if the LTE is not available.
More after the break.

The HTC Titan II will have a 1.5GHz Snapdragon S2 processor by Qualcomm, and the Largest ever on AT&T a 16 megapixel camera ( no that is not a misprint it is a 16 MP camera). The 4.7" screen is among the largest for Windows Phone. No release date.
AT&T will be the exclusive carrier Nokia’s first ever 4G LTE Windows Phone in the U.S. The full info on the Nokia phone will be shared during Nokia’s press conference in Las Vegas at CES.