Others may have posted these facts but i havent read through it all yet:
1. The Nexus is future proof for a little while.. sure the Razr will get ICS, but after that? Nexus phones typically get 2-3 major upgrades before they just cant handle it anymore. Look at the Nexus S... itll be first in line to officially get ICS after this phone launches.
2. The screen appears, both in videos and on paper, to be so much better. Also, on screen buttons add to the screen and as i said above, future proof the phone for future updates.
3. Development - No doubt other phones have great communities behind them, but seeing as how the Nexus is out of the box easy to jump into, the device will have tons of enhanced features and customizations to OS revisions that the Razr wont see for months. Plus this being the first Nexus on Verizon means more devs out there have an opportunity to get their hands on one... be it Gsm/Hspa+ or Cdma/Lte.
Ive always stuck exclusively to Nexus phones and ive never regretted that decision. Ive messed around with other Android phones through friends and family and i just wasnt impressed with Donut when i was on 2.1(Nexus One). I loved having Gingerbread(Nexus S) 6 months before everyone else. Ill surely love having other limited time exclusive updates as well. This is all coming from someone who wants cool new features and loves to beta test things.
If you just want a solid experience, like the form factor, dont have time to wait, or get a warm fuzzy feeling when you see robots, explosions, and high speed chases... The Droid Razr is more than capable.