I have a platinum wedding band that is one surprisingly heavy ring! Still... it's just a ring, so I quickly got used to it. Yes when I compared the 38mm SS in the Apple Store with the 38mm Sport I purchased, the SS model felt heavier... but mostly just when I held it in my hand. Once strapped to the wrist the difference in weight was less noticeable, and I'm sure would disappear completely after it has been worn for a day.
On the other hand I can understand how the lighter watch might appeal to somebody who isn't used to wearing a watch. Even though they would get used to either model, at first the lighter Sport may seem more comfortable... and first impressions matter a lot when making that purchasing decision. Some have also said they can't see the SS being worn for exercise. I'm not sure why it would make a difference as long as the watch strap is properly adjusted. I sometimes wear my 38mm Sport a little loose. Not so loose that it spins around, but when I'm on my bicycle the vibration from the road can make it ride down my wrist to the base of my hand. When this happens it will sometimes have trouble measuring my pulse. This happens even with my lightweight Sport model, but fortunately there is an easy solution: I snug it up for exercise. Doesn't have to be uncomfortably tight... just snug.
I was very tempted to buy the SS. I'm not a fan of gold, so in my opinion the SS Apple Watch is the best looking smart watch on the planet... and I think the Sport is the second best looking smartwatch on the planet. I decided to go with the Sport because I liked the look of it almost as much, and because it was more affordable. At the time I could not rationalize spending so much more for the SS model, but now I believe that I could. If you wear something every day for 15 to 18 hours a day, it's okay to splurge if you can afford it. So I may sell my Sport at some point and buy the SS. Then again I might not. I have a third party brown leather strap, and a knock-off black leather loop, and both look fantastic on the silver aluminum Sport in my opinion. But if I were buying it all over again, and my wife said it was okay, I'd buy the 38mm SS
Sean