Most people get used to one and hate the other. I hate both.

My history with these devices is as follows. I had an iPhone3 in 2008. I busted it in frustration in September 2009. I was going to get a new one but I was given a free Nexus−One in December 2009 so I held off. In December 2010 I was given a Nexus−S. In December 2011 I was given a Galaxy Nexus. Now I just recently bought an iPhone4S. In December 2010 I also purchased an iPod Touch, the retina display version. Also from July 2010 I had an iPad1. The point of all this history is that unlike many people who have only briefly used one system or the other since I've used both systems for years. I hate them both.

What I hate about iPhone:

The lack of freedom the bugs crap out of me. It's not the freedom perse. It's the things an iPhone should be able to do but can't because of that lack of freedom. I could live with it if Apple provided enough ways around those limits.

An Android an app can pretty much do whatever it wants. Nearly everything in the system is replaceable. Don't like the home screen? Install a new one. Don't like the virtual keyboard? There are several to pick from.

There are arguably reasons you'd want to do this even on iPhone. I think something like slidescreen is a reasonable UI someone would want to be the default on their phone. I'm sure there are lots of other innovative ideas out there but we'll never see them on iPhone.

Some of the other things this lack of freedom prevents:

The browser doesn't help non-mobile webpages become readable. A lot of people loved iPhone because it was the first phone they owned that let them browse the *real* web and not just a few mobile sites. That was awesome but reading a website designed for a 1200x1024 computer display on a 480x320 display can be frustrating. Sometimes you have to scroll left and right for every line of some article you want to read. Ugh. Apple's solution is "reader" mode. For some pages a button that says "reader" which removes all ads and side bars etc. It's a great idea. Unfortunately it has 2 giant problems. #1) It requires the entire page to load before it starts. That means you often have to sit there waiting for a while before it will let you click the "reader" button. Time you'd rather actually be reading. #2) It doesn't work on many sites. Android's browser tackles this a different way. By default it restricts the width of certain elements so that when zoomed the text ends up at a reasonable size and word wrapped to match. For example here is Hacker News on an iPhone4S. Too small to read IMO. Double tap and the iOS browser zooms in to get rid of the border but it's hardly any more readable. Zoom in enough to read and you can only see half of each headline. Here's the same webpage on the Android browser. Notice the headlines are word wrapped early. The don't go all the way across the page. Double tap and it zooms in to a readable size. Sadly, translating from the 300+ dpi displays of both of those phones to a ~75dpi computer screen doesn't really cut it. Suffice it to say that when I switched from Android to iPhone recently I started noticing many of the web sites I read commonly are much harder to read on iPhone because of this difference in browser design. Of course many sites have a mobile version. Unfortunately in my experience many of the mobile versions of websites are missing functionality which means I almost always look for the "Full Site" link. For example look up "t3i" on Amazon.com. The entire large product description area is missing on the mobile version. Pick "Full site" at the bottom and now you get the nice large description but it's basically unusable on iPhone at any readable size because of the issues above.

What I hate about Android:

The list is probably larger here but also harder to put into words. The simple answer is Android's user experience is no where near as good as iOS's. The problem here is that for many people this is a subjective judgement. Some examples:

The hardware is poorly designed Android's hardware diversity is both a blessing and a curse. The benefit is lots of choice, lots of competition, lots of opportunities for manufactures to add new stuff. Higher res displays. More memory, faster CPUs, more powerful GPUs, better cameras, etc.. I actually don't subscribe to the idea that that most of that fragmentation is bad. Desktop computers have a million different specs. Laptops have a million different specs. Developers have been making apps for those for decades and not bitching about it. In fact, having used the large Galaxy Nexus for a couple of weeks it's shocking how small the iPhone display feels in comparison. That said there are several hardware problems for me: #1) varying button location. Every new model of Android re-arranges the order of the 4 basic android buttons, back, menu, home, search. It's super frustrating. You have a phone for 1 to 2 years. You get a new one and your muscle memory has you pressing the wrong buttons since they changed the order. Here are the 4 Android phones from Google. The G1, the Nexus One, the Nexus-S and the Galaxy Nexus. Notice the home button, probably the most pressed button has moved position with every new phone!!! Imagine if every time you bought a new computer the letter keys were in a different order or you bought a new car and the position of gas, break, clutch changed. Yes, eventually you'd get used to it. That doesn't mean it's okay to change the order. I seriously doubt someone even thought about this. Probably every phone was made by a different designer and with no rules or guidelines each one did their own thing. #2) touch surfaces that go all the way to the edge Another problem, at least with the Nexus-One, Nexus-S, and Galaxy Nexus is there is no dead space around the edge of the display or rather that dead space is too thin. This comes up all the time when I handle an Android phone. I pick it up and accidentally exit the app I was just about to use. I set it down and accidentally press a button I didn't mean to press. This has happened daily for me on Android for the last 2 years of use. Some examples: I have navigation on in the car. The phone is in a coin area in the center console between the 2 front seats. I try to pick up the phone, if any part of my fingers brushes edges of the display the odds are high it will exit the navigation screen. Especially if it's near the home/back/search virtual buttons. This is especially frustrating while driving because what was going to be a 1 or 2 second interaction with the phone to glance at the display is now a much more involved interaction while I try to get back to the navigation app and pay attention to the road. I start a game. The phone is being held in portrait mode (tall), I rotate it in my hand to landscape (wide) since most games play in landscape. While rotating my finger brushes the back or home virtual keys and the game exits. The same thing happens when trying to play a game. There's a virtual button or joypad but if you slide your finger slightly too far you hit the home or back key and exit the game. These problems rarely if ever happen on iOS because there's enough of a border that it's easy to pick the phone up without accidentally pressing a button and because there are no virtual system buttons. It doesn't help that all 3 of the android phones mentioned above have effectively virtual keys right near the one edge of the phone making them easy to hit. iPhone's design is such that the one physical button is hard to hit by accident and requires a very deliberate press. The phone is thick enough that it's easy to pick up without pressing the screen by accident and there's a enough of a dead space around the touch zone that it's far less likely you'll touch somewhere you didn't mean to just by picking it up or putting it down. I don't feel like this problem will ever be fixed. It's too subtle to get right for pretty much anyone but Apple. Yea, I know that's a ridiculous statement but one way or another I don't believe Android will ever fix this problem. Either they don't get it, don't care, or they can't get the hardware manufacturers to accept it.