The Google version will not have anything that samsung includes stock. No air gestures, look away, scrolling. No touch wiz. S-health, any apps that say samsung will probably not be included. NFC will be because thats part of the hardware and stock android supports it. If your someone that uses/likes all the extras that come with the regular S4 over timely updates then stick with your current S4. The google S4 will definitely get updates MONTHS before the regular version, but some people don't consider that a priority over features.
If Verizon received this phone i would jump on it in a second because timely updates are important to me. Even if i had to shovel out $400 more due to it not being subsidized. But on the other hand, knowing that there will be an AOSP version for the Gs4 will really help getting ports fast for the regular S4 on Verizon. Time will tell.