I had the 41mm for a week and I just got the 45mm in the mail today. I have skinny (6.25” or 156mm) male wrists with about 51mm at the flat part of the wrist where the watch sits.
In my case, the 45mm actually looked better to me, when comparing the sizes you need to look at them from a distance not from up close, otherwise the bigger one may seem oversized. The 41mm watch was okay but the thickness combined with its smaller 41mm size made it look kind of disproportionate, almost chunky. It was the same feeling as when I compared a Seiko SKX007 with the smaller SKX013.
Here’s a comparison between 41mm and 45mm. I’ve also included the Amazfit Bip S for comparison in the middle of one of the pics. It is 42mm.
The one with the green band is 45mm, the starlight bezel one is 41mm.