I had the 8+ for about a month before I changed to X. I think the battery life of 8+ is just slightly longer than X. I personally feel not much diff. The screen is longer than 8+. Somehow, the launching of internet is faster on X. I tried it side by side. Also some X users forgot to deactivate the true tone color and hence seeing more yellowish tint. Once you deactivate the TT, you should see bluish tint which is the spec of OLED (same as Samsung S8/Note 8). The contrast is much better and the holding is great too. I personally feel the 64G is good enough. You can always backup the photos and removed it. I find the bigger the capacity of the phone (you stored more info), the longer it takes to backup and restore, in the event you change another phone. 128G is the sweet spot but Apple is smart, with 64G and 256G avail, most are tempted to go higher where their margins are..
If you have a chance to reconstruct, go for the X. You will not regret it.