As per my opinion..its gonna be
ANDROID
bcoz----
-More choice.
-Open Source OS (makes it better for devs).
-Custom UI's.
-Widgets are amazing.
-Cheaper.
-turn by turn gps
-more customization
-free apps
-available on different brands such as motorola, htc, lg, samsung
ETC.
its more than enough to derive a result.....!!!
