First world problems for sure! I am having the same dilemma and have both models in hand.
I am actually finding the smaller one pretty good, it feels bigger than the S9 (that I did find to be too small) not much but enough to make a difference imo. The single hole punch is also preferable to the double especially as the double brings no benefit to me. Overall it is a pretty big screen in very manageable footprint.
My plus model is the ceramic and it feels sooo nice in the hand far more premium than the smaller S10 but the extra weight coupled with the taller phone does make it slightly awkward to use one handed and I get the feeling it could slip out of my hand at any moment. I wanted the ceramic as I rarely use a case but maybe the lighter glass one would be better? I have used many large phones recently so should have no issue with the plus really.
I have not found the battery life on either to be great TBH, I have used a Mate 20 pro and view 20 and neither of the S10s are as good as these two and the trademark Samsung standby drain is present. So I am leaning towards the S10 at the moment but I fear I will end up keeping both at this rate!
By the way the S10 is slightly bigger than the iPhone Xs not smaller
https://www.phonearena.com/phones/size/Samsung-Galaxy-S10,Apple-iPhone-XS/phones/10959,10766