Hi Richard, I've owned the U1, the Pelagos LHD and most recently the U50 SDR. Sadly not all at the same time though. The Pelagos I'd say wears comparably to the U1 on my 6.75" wrist - for me just a bit too big and overhanging my wrist bone (I think without checking both have a 50mm+ lug-to-lug). The U50 wears much more comfortably to me and is substantially lighter.
I did have the U1 on silicon strap but found the large clasp to be a bit of a beast and it'd constantly be hitting the table when I was using my keyboard. The Pelagos was on bracelet and despite the adjustable clasp I struggled to get a fit that didn't feel a tad too tight when my wrist expanded. The U50 I had on a couple of elastic single pass straps and for me wore the most comfortably on that (although it's worth noting that I've gone completely off bracelets in the last few years).
I'd say all three were noticeable watches (at least I felt they were to others), but in different ways - the U1 and Pelagos purely down to their size, whereas the red accents on the U50 SDR, exacerbated perhaps by the all-black bezel, made it jump out.
For a weight and looks comparison there's some good pics here over on WUS.
Andy