See full review here:
http://fromandroidtoapple.blogspot.com/
I believe that I have come full circle.  I absolutely hated Apple  products (except for basic iPods) up until the iPad came out.  I tried  the iPad out in Best Buy and was amazed.  Ever since, I have been on the  iDevice bandwagon.  I still won't use a Mac computer, but as far as the  mobile devices go...
Anyhow, being that I've been an Android user for so long, I figured I'd  post up a comparison between the two for those thinking of switching but  might be on the fence.
Display
Hands down this goes to the iPhone 4.  Yes, the screen size on the Droid  X is much larger, but the quality is much better on the iPhone and that  makes all the difference to me.  Text, pictures, and everything is much  clearer.  Think about it this way:  would you rather have a 55" non-HD  TV or have a 46" 1080p HDTV...that's about the difference to me, and for  me, I'd pic the HDTV over the non-HD any day of the week.
Keyboard
This is HUGE for me.  The number one frustration I have ALWAYS had with  the Android OS and even aftermarket keyboards is the phone always seems  to lag because I type on it too quickly.  This is NEVER the case with  the iPhone/iPad/iPod Touch and probably the primary reason I switched.
Also, the keyboard works wonderfully.  Somehow, and I can't figure out  how Apple does it, but no matter how big the keyboard is on the Android,  I can always type faster on an Apple keyboard.  It boggles my mind.
In addition, the Apple devices NATIVELY support Arabic keyboards, something that Android devices still cannot do, last I checked.  This is also a huge deal breaker for me.
App Store
As an Android user since it's inception, I can say for certain that the  Apple App Store is far superior.  However, it has also been around for  longer so there is a possibility that the Android store will catch up  some day.  But for now the App Store isn't inherently better, it's just  that there is a bigger market apparently so developers are most likely  to develop an app for iDevices FIRST if not exclusively.  I can't count  how many times there was an awesome app in the app store that I waited  over a year for to come to Android.
The downside is, many apps on the Apple Store are more expensive than  apps on the Android Market.  For example, you can get Google Sky Map for  free on the Android Market, but you have to pay for some sort of  equivalent on the App Store.
I still find the App Store far superior.
Navigation
Hands down, any Android device wins in this category.  The iPhone has  some great GPS apps available, but most of them are between 30 and 60  dollars, whereas every Android device comes with Turn by Turn Google  Maps navigation...something I never felt the need to stray from.  Right  now I am using a cheap (or maybe it was free?) Mapquest Navigation app  for the iPhone.  It works decent, but it's nothing as good as Google  Maps TBT that comes with Android.
Speech to Text
Nonexistent on the iPhone and Dragon Dictation is worthless, so hands down this goes to Android.
Fragility
The iPhone definitely seems less durable than my Motorola Droid X.  It  also looks more quality, but if you drop it, I'd say you're done for.  I  bought the Square Trade warranty for $99.
Widgets
Most people say that the Android has widgets and that makes it better,  but frankly, most Android widgets suck and just drain the battery so I  don't miss them at all.  Yeah you can have the weather right on your  desktop, but I can get the weather from an app in one click.  If you're  jailbroken you can add the weather to your lock screen anyhow.
Fluidity
I don't know how they do it, but no matter how fast of an Android phone  I've had, nothing compares to the lagless nature of iOS.  I've  overclocked my Android phones, optimized, you name it.  Still not as  seamless as iOS.
Loudness
The iPhone seems to be a lot louder than my Droid X in terms of  ringtones and call volume.  This wasn't a deal breaker for me by any  means on the Droid X but it was worth mentioning if you have that issue.
Notifications
The Android devices tend to have better notification systems.  The pop  ups on the Apple devices can be annoying and of course most Android  phones have some sort of LED that let you know you have a notification  without having to turn on the screen.
Camera
Despite the megapixel difference, I don't notice a picture quality  difference.  If I want to take a high quality picture, I'm not using a  phone camera anyhow.
One thing I thought would be irrelevant to me would be the front facing  camera.  But as it turns out, having one is just awesome.  I use  FaceTime all the time because I live thousands of miles away from my  family.  Today I chatted with my cousin while she was at my  grandmother's house and I was able to see them for the first time in  months and I also gave them a tour of my new house.  Very spiffy.
If you aren't frequently separated by distance from your family/SO this  might not be a huge deal to you, but it's a pleasant surprise for me.
Email
If you have GMail, the Android phones are going to be inherently better  at handling your GMail.  However, I had many problems with the GMail  application on my Android device, and I wasn't alone.  No solution was  ever really found, but sometimes at random messages would get stuck in  the outbox even when on full signal with wifi.  It appeared to have  something to do with the way Android OS handled cache but we never  really pinpointed it.  It was few and far between, but it happened.
Facebook
I know some old geezers hate Facebook, but the Facebook app for the iPhone is infinitely better than the app for Android.  You can tag photos, and actually get regular notifications, unlike the Android version.  Why such a difference I have no idea...
Reception
EDIT: I went into the office today where  I NEVER had signal with my Droid X.  I would have to lean out the  window just to send a text.  Today with my iPhone I texted, played Words  with Friends, got emails, sent emails, and made a few flawless voice  calls.  I was the only one in the entire office (including one of my  NCOs that has a Droid X) that could do any of that.  Everyone else had to go outside to make calls.  Granted, my battery drained like a mofo, but it was too easy to plug the phone in next to my desk.  People were borrowing my phone all day to make calls to soldiers.  Very odd that this should be the case, but for whatever reason it is.
Flash Player
This was always a huge contention to people, that the iProducts can't play Flash.  I had Flash on Froyo 2.2 Browser on my Droid X and it was HORRIBLE.  Make no mistake about it, it's about money for Steve Jobs/Apple, but at the end of the day he is still right - Flash is garbage on mobile devices.  Period.  Most websites with Flash have flash ads, flash banners, flash menus, etc.  The phone ran like utter crap trying to process all that junk.  Most of the good websites have HTML5 anyhow - even the porn sites.  lol