I have both Galaxy S and IP4.
For me, I need to log in a few webpages quite often.
IP4 provide me better compatibility.
Its stability is obviously better than Android.
And I like the retina display more as it provide solid image with more detail but the color is a bit pale with compared with Super Amoled.

Honestly, I like Andriod's flexibility e.g. Sharing files thru BT, More System settings, Faster web browsing(My feeling only).

Finally, coz of the web application compatibility I am using IP4.
I keep the Galaxy S and waiting for 2.2 upgrade.

So, u need to think about what u need , then u choose what it suits.