From the front, the two phones are indistinguishable. Both have that huge tract of Super AMOLED HD goodness (aka a 4.65-inch display), ear speaker and front-facing camera. The power button, volume rocker and charging contacts are all in the exact same spots. Or at least close enough that we can't tell with the naked eye.
Flip the Verizon Galaxy Nexus over, and it's almost identical to the GSM version. The Google logo has been traded in for a Verizon 4G silkscreen. Note that the GSM battery cover is not interchangable with the Verizon version. The tabs that hold it in place are in slightly different positions. So if you have to have that Google logo, you're going to have to work at it a bit.
Open the battery cover on the Verizon Galaxy Nexus and you find the biggest visible physical difference. It uses a different battery than the GSM version -- different shape, and it's been upped to 1850 mAh capacity. Verizon's using a micro SIM card for LTE, and it's in a different location, too. You'll also find screens and other design differences back here.
That's it for the outside. The internals, of course, are the same, only with a CDMA radio and 4G LTE radio. (Oh, and there's a subtle Qualcomm 4G sticker advertising that fact on the bottom bezel.) Otherwise, same 1.2 GHz dual-core processor, 32GB of storage and 1GB of RAM.
We've got more hands-on video and pictures after the break, and a full review forthcoming.
Youtube link for mobile viewing