I went through the same comparison about a month ago when I got my Maxx. Between the two, there's not much to differentiate them strongly from each other. A spec here, a removable battery there. Even the size difference didn't seem as significant in my hand as I expected.
The killer feature for me turned out to be the huge battery in the Maxx. It is massively powerful. I no longer plug in my phone when I'm using navigation for less than an hour. I don't nurse the battery all day as I used to. For the first time yesterday I managed to run the thing below 20% -- because I had the screen on doing web browsing in a low-signal area nearly all day. (And 20% is still several hours ...)