I'm considering going with the 8 plus as well for the following reasons:
- The X has a later release than the 8 and 8 plus
- Lack of availability will likely push the chance of getting an X into 2018
- This will mess up my annual upgrade schedule with AT&T. What happens when the next generation X comes out in September of 2018 of next year, but I didn't get my current gen X until early 2018? You will find your self upgrading in the middle of an upgrade cycle every year.
- I'm not a big fan of the notch. I might change my mind when I hold the X, but just on ordering sight unseen, I don't like it.
- The 8 plus gets slightly better battery life than the X.
- The 8 plus shows more information on the screen than the X. The X has the bigger screen, but it is more narrow, which will affect how much information you can seen when browsing.
Having said all of this, I would go for the X if it were available this weekend. The big deciding factor for me is the lack of availability and messing up my annual upgrade schedule. These are just my reasons, and everyone's situation and needs are different.