You need to give a tad more information.

Describe what steps you are doing on the N900 and what it is that makes you feel the 'signal' qualities are different between the two devices.

All GPS units will take at the very least 15 minutes to get a valid first fix. (No comments about sirf star III chipsets - they use predictions, not actual fixes in those first minutes) - fixes will just take seconds to a few minutes after the first fix.

To mitigate this delay, you can use A-GPS - fixes will then only take one or two seconds regardless of GPS state, assuming you have a good internet connection.