Managed to get my hands on the 3/XL earlier today in a CPW. I'd already pre-ordered an XL, but wanted to try one out for size before it was too late to change my mind.
Both actually seemed smaller than I thought they would, even though the 3 is on paper the same size as my S8 - it felt a little smaller than I'd imagined. I actually preferred the size of the XL, I typically don't like the larger phones but seemed well proportioned.
Both screens seemed decent, I didn't try out the different colour modes (sRBG/adaptive etc) but they both seemed up to par of the current flagships.
The textured glass back wasn't what I was expecting, a little slippery but at least not a fingerprint magnet. Definitely nicer than just a typical glass back.
Build quality wise they were both every bit as good as my S8, and (IMO at least) the iPhone X/XS.
The notch, didn't bother me at all. When using it, I didn't really notice it that much. A couple of apps just blacked it out anyway. In photos it looks really stark - but in use it's not really something I'd be concerned about based on the brief play I had with it.