Interesting question which surfaces every now and then .. personally, I reckon a silver bird looks absolutely ripper.
Main Advantages
(a) significant weight and associated painting cost savings
(b) looks great - possible marketing tool.
Main Disadvantages
(a) aluminium is quite reactive and forms a surface oxide any time the metal is exposed to air - this is the basis for anodizing - colour the oxide and you get a nice coloured finish. Longer term polishing progressively has the associated risk of sheet damage. (We can exclude the idiots who feature in the tale about the car dealer who wanted his nice new aircraft polished up - just a little problem with all those tiny bumpy bits over the skin - never mind, grind off the rivet heads and the problem went away ..... thank heavens for the Darwin Awards to give us a vehicle to put such stupidity on a pinnacle when it is fatal).
(b) lots of lap and other joints just asking for corrosion problems to be accelerated compared to a nicely painted surface.
Which wins ? .. the numbers give the clue.