The Razr is thin and durable, and has a non-pentile (I think) AMOLED display. Other than that the Rezound is as good or better in every way. Because the display is only qHD, the Razr actually looks smoother sometimes. Someone had installed Launcher Pro on a demo model that I played with once, and it was pretty damn smooth.
The Rezound has a better camera (especially for Macro and low light shots), and a higher definition display. It has a removable battery...this is important, because it means you can easily install extended batteries. My Rezound has gone 24 hours between charges before, and can easily go 12 hours with heavy use (4g, full brightness ect). The non-removable battery and non-HD display are the main reasons I would pass on the Razr.
As far as rooting, the two phones probably have similar amounts of developer support, but the Rezound will always be easier to root because HTC allows you to unlock it if you want. So you never have to rely on hacks to do it. Motorola is notoriously obnoxious about roadblocking rooting efforts on their phones.
Beats audio is IMO a gimmick. It does sound nice, but it is nothing you could not replicate on any phone with an EQ. And I don't think the current Rezounds come with the Beats earbuds anymore (I did like those...I use mine all the time still).
So between the two, I would say go with the Rezound. Especially since this is not the Maxx version of the Razr.