Another (improvised) test.
Unplug from dc at 12:00, both the iphone 3gs and the n900.

The iphone, with 3G activated. The n900, with offline (airplane) mode, cause I wanted to keep battery.

13:45, I take the iphone to search some web page. Before, I see the battery. Wow, a 97%, impressive.

14:00, I take the n900, I put it in online mode. Let's see the battery (starting from the typical 96%). Wow, a 89% (!), with airplane mode?

I really didn't expect such battery drain when the phone is just doing nothing at all. Or in the opposite, I didn't expect the iphone to be almost at the 100% with 3G (but no data connections) activated.

More tests ongoing.