I don’t have the LG Expo or the Samsung Captivate but the iPhone is a great device. I hope this doesn’t sound fanboyish but I can tell you about my experience with my iPhone 4.
The texting is great. Many disagree with me when I say I like the software keyboard on the iPhone better than I do a physical keyboard but once you get used to it and embrace the smart keyboard you’ll type faster than you ever would on a physical keyboard. This is because you barely need to touch a key to enter it and because of its auto-correction, and spell check too.
The smart keyboard even learns how you type to correct you more accurately. Many people also don’t know this but after it starts to learn the words you use most while you type, certain letters get bigger making it easier to tap then. You don’t see it on the screen but there is a bigger space around those specific keys to touch. Hope that made sense. And you can even connect your hardware keyboard!
The camera is excellent. There is even a front facing camera. Here are some test shots. I don’t think I need to say more.
As for business, I can’t really say since I don’t use it for business but the iPhone is being used in more and more corporations and the phone seems to be very secure. The only thing missing is Office or iWork if you’re into that and rumour has it that Apple will make an iWork version for the iPhone similar to the iPad version.
Other than that all I can say is it’s a great phone, no reception issues here in Canada, great battery, and really fast. Hope that helped!