You will not be able to update the china region cameras...there are differences in the design of some models as well, like the turrets where US cameras are a sturdier design...
Fenderman has made a very good point. It seems to me that one needs to flash the camera only if the new firmware repairs a existing camera defect...or if the new firmware adds a new feature to the camera. However, when one uses a third party video management system with the camera it is the vms which does all of the work (such as motion detection) and all the camera does is send images to the vms for processing. I've got a bunch of cameras and the only reason I've ever updated the firmware on them is because I couldn't leave well enough alone...not because there was an issue which needed correcting or a new camera feature I needed. My hope was always "Gee I hope this firmware update makes the camera provide better images" but I never saw that happen.
No the cameras are identical except for the region they are set to (shouldn't be a problem if you order from aliexpress as they should already be hacked).
I've used varifocal cameras before, I agree they are a pain to get focused at first, but once you do they are fine.
I take it you are referring to DS-2CD2722FWD-IZS, I'm not finding it at that price. I have found the DS-2CD2732F-I(S) for around that price (supposedly). I keep finding where people are showing a retail US box in the picture, but hearing people are receiving brown box Chinese when they get them from different various places. That's why I was originally asking, other than warranty, is there any real advantage? Warranty is relative, if you wind up getting the cameras for half the price, and have one fail, you are still way ahead on cost. Over the years I've had to warranty very few cameras fail in the warranty period (and other equipment at that), probably my #1 failure across the board in warranty period has been power supplies.
I have looked at many camera suppliers, even ones I've seen suggested here. I think I found the thread, just request a catalog? or ???