The HTC Amaze 4G smartphone.

T-Mobile will sell the HTC Amaze 4G for $259.99 and the Samsung Galaxy S II for $229.99. Both prices are after a $50 rebate and with a two-year contract.

They will be the first T-Mobile's smartphones to run on the carrier's HSPA+42 4G network, which has a theoretical top download speed of 42Mbps. T-Mobile said average downloads on the network approach 8 Mbps.

What most distinguishes the devices, however, is the Qualcomm Snapdragon S3 chip, a 1.5 GHz dual-core processor. The Amaze runs Android 2.3.4, also known as Gingerbread, while the Galaxy S II runs Android version 2.3.5.

Both phones support near field communications technology, which is being used for emerging mobile wallet in-store purchasing.