If you are thinking about buying one of those phones and you are not sure which one, here are some things to consider:

HTC Diamond: 102mm in height, 51mm wide, 11.5mm thick, weighing 110g.

Apple iPhone:   115mm in hight, 61mm wide, 11.6mm thick, weighing 135g.

HTC Diamond: 480 x 640, 2.8" TFT LCD touch-sensitive screen

Apple iPhone:  480 x 320 3.5" multi-touch display

HTC Diamond: Windows Mobile 6.1 Professional with TouchFLO 3D technology

Apple iPhone: OS X

HTC Diamond: 4GB internal flash storage, 192 MB DDR SDRAM, 256 MB ROM. A microSD card slot is supported, for additional storage.

Apple iPhone: 8GB or 16GB flash drive, 128MB of RAM.

HTC Diamond: 3.2-megapixel sensor, and auto focus camera + a second camera on the front, VGA CMOS color camera, for video calling.

Apple iPhone: 2.0-megapixel sensor, and no auto focus camera.

HTC Diamond: Integrated speaker and FM radio, supports MP3, AAC, AAC+, WMA, WAV and AMR-NB formats.

Apple iPhone:  AAC, Protected AAC, MP3, MP3 VBR, Audible, Apple Lossless, AIFF, WAV formats.

HTC Diamond: HSDPA connectivity, 384 kbps up-link and 7.2 Mbps down-link speeds.

Apple iPhone: Just the regular slow internet, (second generation iPhone shold have 3G).

HTC Diamond: GPS and A-GPS.

Apple iPhone: No GPS at this time.

HTC Diamond:  270 minutes of talktime for WCDMA and up to 330 minutes on GSM networks. Standby time 396 hours and 285 hours respectively. Video-calling users will get up to 145 minutes on WCDMA.

Apple iPhone:  Up to 8 hours of talk time, up to 250 hours of standby, 6 hours of internet use, 7 hours of video playback, and up to 24 hours of audio playback.