Sendation strength is its sense user interface actually and camera wise it is good ( many websites have reported many problems in this cellphone ) it is dual core it fells good in hands very comfortable stable user interface .
Sgs2 strength is its multimedia capabilities , camera , display , less weight .. touchwiz new version is quite better than the previous one
Iphone strength is its audio capabilities specially and apps and easy to use interface
i can gurantee the number of quality apps in IOS are far far greater in numbers than andriods for sure
i had 2g 3g 3gs 4 then i jumped to andriod i downloaded torrent of 600+ apps for andriod and installed in my tablet galaxy tab , x10 thn i felt much difference in them but for new i will not matter 
you will get
Sensation = 46k new used me ik 41k ka b dikha tha
SGS = 54k new used me 40k set charger
Iphone 4 = 16gb 54k new and white one is 60k factory unlock
otherwise you can get iphone 4 SU or Iphone 4 unlocked by givey sim in 40s or even in 30s
35k me iphone 4 mil rha tha givey sim k sath banda day rha tha 35k me
eid chali jai phir he lena abhi prices hyd me tu ajeeebo gareb he hai
