Omnia is far far better than diamond since it has:
1. Much better camera - one of the best top 3 5MP cameraphones on the market
- 5MP vs 3.2MP
- LED flash vs nothing
-smile detection and other options vs nothing
2. Much bigger display
3. Better memory storage - 8 times more than diamond 16GB+16GB on card
4. Faster processor
5. Omnia is the best phone for GPS and navigation

My vote go for the Diamond. Diamond wins both design and features.