Just thought I’d share my experience in case it’s helpful for anyone. I was pretty certain the 42 mm was going to be too big for me. For a man, I’m on the smaller side and thin and have relatively small wrists. I had seen the 38 and 42 versions in the store in the past (although not recently) and used the size comparisons in the Apple store apps to compare before pre-ordering my S3. I currently wear a Fitbit Charge 2 with a small size wristband. Well, my 38 mm came yesterday and my immediate reaction (as well as my wife’s) was, that is just too small. I think the thing the size comparisons in the app don’t show effectively enough is the curvature of the sides which make the watch face not feel as big once it’s on. Returned the 38 mm last night in store and tried the 42 mm on in person - definitely the better size. Of course, I have to wait another 3-4 weeks to get it now, but that’s ok. I’d rather have the right size. Lesson learned - even if you’ve seen the two sizes in person before, if it’s been some time and you’re not absolutley certain which size you want, go to the store and see which one is better for you. Ok, hopefully my story helps someone out there.