Oh. My. God.
The difference in user experience is astronomical. I work in the tech industry and I train users on how to use my company's software, and I could not for the life of me wrap my mind around some of the most basic aspects of the phone. Most functions, from scrolling and animations to simple things like changing the focus from a text box on the web page to the URL bar of the browser, had noticeable lag. Sometimes the lag was so atrocious that I could not be sure if my taps worked. Occasionally I would get impatient and tap again, and it would register two taps simultaneously and treat it as a double-tap! You are absolutely right that it felt like using a regular computer - and old and slow one. I couldn't deal with it.
At one point I was checking my work email and had to access a voicemail that arrived as an attachment. I clicked it, and instead of playing the voicemail right away (which the iPhone does), the S4 downloaded it as a file. Okay, fine, I get it, you want to pretend you're a computer. But where the hell did it go? Is there a separate browser area for downloaded items like in Chrome? Is there a desktop, or some kind of folder? And if you're pretending to be a computer, am I going to need special software to be able to open this file? Are you really going to make me open another tab and Google "how to find downloaded files on Android"?!? WHY ARE YOU MAKING ME THINK? WHY ARE SIMPLE THINGS NOT OBVIOUS LIKE THEY ARE ON IOS?
In my experience, people are drawn to Android don't care much about user experience and instead want larger screens and tons of features. Personally, I view my smartphone the way I view my car: I want one that is easy to drive, responsive and won't lag for ~2 seconds every time I do something.