Let’s do a quick no biased comparison on these two, shall we?

Display

iPhone 3G: 480 x 320 Touch Screen

HTC Diamond: 480 x 440 Touch Screen

Winner: HTC Diamond

Camera

iPhone 3G: 2M pixel

HTC Diamond: 3.2M pixel

Winner: HTC Diamond

Video Recording

iPhone 3G: No

HTC Diamond: 640×480, 320×240, 176×144

Winner: HTC Diamond

Bluetooth

iPhone 3G: Limited

HTC Diamond: Supports stereo headset, file transfer

Winner: HTC Diamond

WiFi:

iPhone 3G: Yes

HTC Diamond: No

Winner: iPhone 3G

GPS

iPhone 3G: A-GPS. Google Map. No turn by turn navigation.

HTC Diamond: A-GPS. Supports turn by turn navigation with real time traffic.

Winner: HTC Diamond

Memory

iPhone 3G: Built-in 8GB or 16GB

HTC Diamond: Internal 4GB. Supports external memory

Winner: iPhone 3G

Music

iPhone 3G: iTune

HTC Diamond: Windows Media Player and Sprint Music Store

Winner: iPhone 3G

Voice Dialing

iPhone 3G: No

HTC Diamond: Speaker Independent

Winner: HTC Diamond

Mobile TV

iPhone 3G: None

HTC Diamond: Sprint TV

Winner: HTC Diamond

3rd Party Software

iPhone 3G: Apple AppStore

LG Dare: Supports Java applications

Winner: iPhone 3G

Price:

iPhone 3G: $199 with 2 year contract

HTC Diamond: $249 with 2 year contract

Winner: iPhone 3G

Service:

iPhone 3G: AT&T Exclusive in US

HTC Diamond: Sprint (for now, Verizon later)

Winner: Even

Overall Winner: HTC Diamond