good built in quality
design
looks
audio both with speakers and hands free
price
1-both
2-W580
3-W580
4-more or less same
5-W810
w810 and w580 both are good for sound quality and have excellent sound from the speaker.
but w810's cam is better and has AF and flash.
good built in quality -> W810i
design -> w580i
looks -> w580i
audio both with speakers and hands free -> w810i
price -> w810i
If you are okay with w810i, go ahead and get it. Moreover, W810i has autofoucs camera, LED flash, sturdiness.
w580 has two features: shake control and led lights on the sides which you wont be using so much. its just for advertising purposes
w810i is good overall
good sound quality, built in quality, batter cam and cheaper
its looks beautiful in white
but i think it is not available here in india, is it? and what about k550i?
Other than that what has been mentioned, w810 has an age old system software and you should avoid it unless you have a special reason. Also W580 has larger, better-looking & high-resolution screen than W810