I hate to be the bearer of bad news, but I will say this once again here, like I do everywhere else:
While the X is only slightly wider and slightly taller, it will be different. It's not just a difference in mm, cm, inches, etc. For the height, that may be true, just slightly taller, slightly further you have to move your finger to get to the top. Width will be a bigger issue though. The reason why is because your hand's dimension's are finite. Your hand/fingers can only stretch so much, and the more stretching you have to do, the more uncomfortable it is. So while it may only be 3-4% wider if it's already at the limit your thumb can reach for one handed use, then it may even seem 15-20% less comfortable. I'm not saying those numbers are right, but that's the idea behind it.
I personally still find the 7/8 to be a bit too wide for comfortable/proper one handed use and that bothers me when coming from the 5S/SE form factor, even though I have big hands. Height is not an issue, it's the width.