Unanswered: Samsung galaxy S?

Hey! i am a newbie and to be honest I don't really understand a lot about smart phones...
So my girlfriend Gosia would like one for her B-day and I don't really know what to buy....should I go for the classic iPhone4? but it's kinda expensive...
(cheapest i found it's around 600 here....
shoppydoo .
co .
uk/prices-cell_phones_calling_plan-iphone_4.html)
Or maybe there is an alternative? Anything nearly as good but a little cheaper? How about the new Samsung Galaxy S?

thanks experts!!!!!
PP