It seems some see this as a contest in which the only acceptable outcome is a consensus of one phone being godly and the other being horse manure...
I'll echo what many have said and say that you should go to a store and try them both out (and definitely go for the MAXX if you want the razr). The razr has a skinned version of Android, and while it's not as bad as Motoblur has been in the past, you may prefer stock. If you're into rooting, get the Nexus, hands down. Much easier to root and unlock, and a much more active dev community. Also, if updates are important, get the Nexus. Sure, the Verizon Nexus won't see official updates as quickly as the GSM version, given that Verizon tends to drag its feet in the testing process, but we'll get Jelly Bean a hell of a lot sooner than either version of the razr will.
On the other hand, the razr is reportedly much more durable, and the MAXX has awesome battery life. Motorola has a good reputation for radio quality as well, although tales of the Nexus's signal issues are greatly exaggerated (unless you're hearing them from an unlucky recipient of a defective Nexus, but if that happens to you, get a warranty replacement). I really haven't had any issues with signal quality with the Nexus, and have never dropped a call. It works pretty well as a phone, and people on the other line say it's a noticeable improvement in sound from my end from my old Dinc.
Also, note about the S3: yes, there is a "developer edition" without the locked bootloader that will be sold directly from Samsung. However, to my knowledge, this will not be available for a subsidized price with a new contract, you will have to pay full retail price (about $600, if I'm correct) for it.