Depends how you use the phone.
I personaly have fallen in love with iOS. Nothing beats the vast number of apps on the Apple app store. Developers love to make apps for the iOS as not only iphone users use them but also a great number of ipod and ipad users too.
The apps on Android fall a little short (others are just too far behind).
iPhone being one of the most famous phones - its allways in the spotlight, so it gets a lot of accessories, updates, apps and hacks etc. You'll never feel that ur missing out on an experience.
Camera is ok - good enough for occasional use. Sound on speakers is not bad (a GREAT improvement over the 1st iphone) but maybe ARC and Galaxy might be louder (just guessing). Music sounds great through (third party) headphones! You can also find a lot of speakers that are iphone/ipod ready. So thats a nice plus if ur looking into spending for accessories.
And I think its comparatively a little cheaper to the other 2 ur comparing with.
BTW - there is one major drawback - a new iphone is announced every summer. So ur iphone4 wont stay topdog for long!
just my 2 cents - again it all depends how u use it!