well... this comparison is bound to come out some time, it's inevitable.
here's a couple of what I've found in the net...
a feature comparison
20 reasons
comparing the two
in my opinion, it's a matter of taste... if you're perfectly happy with what the iPhone gives you, then there's really no need to look at another phone. On the other hand, if you're not happy with the iPhone, and you have a need for the added features of the 5800 - then the 5800 might just be for you indeed.
cheers!