I finally got the answer.... the new iPhone 5s A1533 can support both Verizon and AT&T. Apple was able to pack both CDMA, GSM and all the LTE bands Verizon and AT&T support. If you buy your iPhone from Verizon or AT&T you will be getting the same exact phone (model A1533).
Here's the difference..
If you buy your phone from Verizon and decide to put in a AT&T SIM card it'll work no problem. But if you have an iPhone you bought from AT&T and try to activate it on the Verizon network, Verizon will check the phone and if it's not registard with them as Verizon phone (they have a list) they will refuse to activate it on their network.
If your buying off contract at full retial and want the option to use either the Verizon or AT&T network buy the Verizon branded iPhone. This will give you flixability to use mutipale carries in the future.