For me, my decision started with brand name. I love Motorola. They build their phones very, very well, and they are significantly less destructible imo than the crappy plasticy phones that other companies make. I'm clumsy and drop everything and I just wasn't willing to risk it.
Secondly, I can't stand the UI that comes with HTC phones. I think it's ugly. But hey, some people like it. I like Moto because it's sleek and simple if you can ignore the blur (which, admittedly, drives me nuts).
Thirdly, it came down to the specifications and reviews. And... Well, just the beauty of the RAZR. It's just as lightweight as it is thin, but not in a cheap, I'm-gonna-split-in-half-and/or-shatter-if-you-sit-on-me way. The Rezound was huge in comparison. Not something I would want to have in my pocket. Yes, the RAZR is big, but it's not thick, and that makes it much better, at least to me. And don't get me started on that amazing screen. =)
You just have to decide which specifications and brand characteristics are most important to you. I might have gone with the Nexus if it wasn't made out of flimsy plastic. That screen is incredible and I would love to have ICS right now. But instead, I went with a brand that is tried and true, which I've had for years (and remembering back in the day, how long my flip phone Razr lasted me, even when I ran it over with my car, in the snow), and which got great ratings. You just gotta choose.