They're fixed, but all at an angle, so they should provide pretty good 360 degrees coverage.
Well I like that you mentioned this. However just looking, you can't even find the XT12 for sale anywhere, only the ET12. Which would currently cost $200 more than two GT-AX6000 routers.
ASUS XT12:
Pros
1. I like the design, tall but no where near as wide as the GT-AX6000
2. Shelf appeal is definitely in its favor if you can't hide it
3. Tri-Band Wifi
Cons
1. No USB support at this price point is a bit crazy
2. Only three 1gbps LAN ports
3. Big issue can't find a buy option anywhere currently
ASUS GT-AX6000
Pros
1. USB support
2. I know the current cost of two of these are $700 before taxes XT12 cost???
3. Best buy actually carries them right now which is where I prefer to get my router if return is needed
Cons
1. Size compared to the XT12 is a problem need plenty of room and shelf appeal isn't there
2. It is Dual band wifi vs XT12 Tri band wifi
Currently this is what I can think of, probably missing a thing, or two, between the two. Biggest takeaway from all this, I can't even find the XT12 to buy it, if I wanted to right now. Which is a big reason I'm back to considering buying two GT-AX6000, vs the GT-AXE16000. The two AX6000 setup would require me to spend a little over a $100 for a 5 port 2.5gbps switch. Even with the XT12's I would need a switch as well.
Anyways I really do appreciate Merlin bringing up the XT12, I like having a little discussion before making a costly purchase I'm planning to make soon. Merlin if you have anything else to add, that I might be missing, please post it. Also if anyone else has anything to add/opinion on this, post it, I'm happy to read it.