Nokia Lumia 900: 395 cd/m2, 4.4% reflectance
Lumia 920: 600 cd/m2 (listed), ? reflectance
Galaxy S: 354 cd/m2, 4.4% reflectance
Galaxy S3: 224 cd/m2, 5% reflectance (yes I double checked this. The S series delivers progressively worse outdoor performance the further you go:
http://www.displaymate.com/OLED_Gala...ShootOut_1.htm. The compromise is in increased battery performance, as AMOLEDs guzzle power. This makes sense because longer battery life sells more phones. Duh.)
iPhone 4: 541 cd/m2, 7% reflectance
iPhone 5: 556 cd/m2, 4.6% reflectance
Brightness and reflectance are complementary; the more of one you have, the less of the other you need. If Nokia can deliver a display close to that brightness, it should edge over the iPhone 5 even if the reflectance doesn't change (though it's claimed that the new display delivers lower reflectance).
Sources:
http://www.displaymate.com/Smartphon...ShootOut_1.htm
http://www.displaymate.com/Smartphone_ShootOut_2.htm
http://www.displaymate.com/Mobile_Br...ShootOut_2.htm
http://www.phonearena.com/news/Nokia...bility_id29918
http://www.phonearena.com/news/Here-...-works_id26552
http://www.phonearena.com/news/The-N...Snooki_id34169