I have been researching this topic heavily lately and came to the following conclusions from various forums (mostly XDA):
-Wi-fi GT has a weaker GPU and a slightly weaker (or at least just different) CPU. Supposedly it struggles to play back 720p videos and cannot handle 1080p videos at all.
-Wi-Fi GT has Bluetooth 2.1, the 3G versions have BT 3.0.
-Wi-Fi GT may not enjoy the same community/ROM/developer support the 3G versions have had
XDA comment here:
http://forum.xda-developers.com/showpost.php?p=12990116&postcount=12
Overall, I would have gone for a wi-fi version if it came in black (hate the white back) and was $50ish less. Otherwise, you are better off buying something like a Verizon version on a month-to-month plan for $80 more than the wi-fi version. Or get a GSM version to enjoy more ROM possibilities and the internal 16GB vs. 2GB on the CDMA versions.
P.S. I love the GT formfactor. The HTC Flyer might be appealing but otherwise, every new tablet I've seen is too big and/or thick and heavy for one-handed use (primarily multimedia, web browsing and e-books). I replaced a Nook Color with the GT, for what it's worth.
I've love to see a refreshed 7" GT with a standard micro-USB & micro or mini HDMI connectors, thinner body, at least a 1.2Ghz CPU, and Gingerbread (if not Honeycomb).