quick night time photo tests under exactly same condition with flash off and default settings and another disappointment from my beloved N900 and I'm aware of 3MP diff but still .. Sorry about how I've put it coz was too lazy to put both in flickr and link here
Couple things exttacted from details:
Xperia
ISO 1000, focal length: 4.7mm, exposure bias: 0.00ev, exposure time: 0.067 sec, jpeg quality 99.1

N900
Iso 800, focal length 5.2, exposure time 0.066 sec , jpeg quality 85.5.

Xperia


N900