The HTC Touch Diamond and Samsung i900 Omnia are two devices that go head to head with the iPhone 3G in terms of features and specification and are expected to give a tough competition to the successor of Apple's trend setting device.

GSM Arena has recently posted a detailed review comparing the HTC Touch Diamond and Samsung i900 omnia. I personally think that it will be unfair to say which device wins and which loses as both devices have their own strengths and weaknesses. I would also have to say that choosing one device over the other is sheer matter of personal preference and judgement.

Here is a summary of the Review comparing the two devices:

Diamond Strengths:

The Diamond goes ahead of Samsung Omnia due to the following factors:

The Diamond has a better display and comes with a dedicated 64MB chipset.
The Diamond has a better design, more compact body and lighter weight as compared to Omnia.
Diamond's TouchFLO 3D technology is better than Omnia's TouchWiz Technology. Similarly Diamond's Touch-sensitive scroll wheel is more useful than Omnia's optical joystick
Active Magnetic Stylus is a plus point on the Diamond whereas it is missing on the Omnia.
Diamond comes with a Standard miniUSB slot which offers more flexibility.
The Diamond has a better video playback performance.

Omnia Strengths:

The Omnia goes ahead of Diamond due to the following factors:

The Omnia has a bigger display size.
The Omnia has a more solid build as compared to the Diamond.
The Omnia comes with double the battery life as compared to the Diamond.
The Omnia has a better CPU performance.
The Omnia has a better and more powerful camera.
The Omnia comes with 8GB/16GB memory and microSD slot whereas the Diamond comes with only 4GB memory and no microSD slot.
The Omnia comes with Quadband GSM Support whereas the Diamond has two versions to support all the four GSM bands.
The Omnia also comes with TV-out, Landscape QWERTY Keyboard, Auto screen rotation and DivX support which are missing on the Diamond.

Source: GSM Arena