I plan to go and buy a nokia 5800 tomoro... I know the new iphone 3g s is comin out in august...?

Can anyone give me a nice reason why i should wait for a couple of months to buy the iphone rather than 5800? I asked this quest b4 but got onl;y short answers supporting iphone... no one was able to explicitly state a proper reason for me to wait.... can anyone help me out?