If you want to go for BRAND value and features then nothing can beat the Android and Samsung combination.Android has more apps,games more features and above all a well set operating system plus Galaxy y duos is a very good device with 1GHZ processor and 512mb ram
Where as Lumia 620 is a windows phone which has only a handfull of apps working on it plus only a single sim phone.There is still years till we can see a completely app ready windows phone.so in that case better go for SGS DUOS
But if u can compromise of brand name then u can also go for MICROMAX A110 etc