I had my series 0 Apple Watch Sport for about 2.5 years, since it's original launch. At the time, the sport models came only with the composite (i.e. plastic) back for the heart rate sensor. When it came time to buy my series 3 Apple Watch Sport, I opted for the $70 more expensive version with cellular because it was the better quality watch, as it featured a ceramic back and an additional 8 GB of storage space. I have no intention of ever using LTE, but at least I have the option should I change my mind. Here is a picture comparing the composite back on my S0 to the ceramic back on my S3. You can see how scratched the composite back has become over 2.5 years of use, presumably from the contact between it and the charging puck. Since ceramic is at an 8.5 on Mohs scale of hardness (with diamond at a 10), it is very likely that the ceramic back on my S3 will never see a single scratch. To those unaware, the LTE version of the S3 Apple Watch Sport features a ceramic back, 8 GB more of storage, and the option to use LTE, while the GPS only version has a composite back and only 8 GB of storage.