Question about Garmin Fenix 6 Sapphire

Yes, the only difference is the sapphire-glass.
Sapphire-Glass is a lot harder and way more scratch resistant then Gorilla Glass 3. It is considered premium on normal watches.
I wouldn't pay the extra 250 just for the sapphire for several reasons.
1. Lifespan: -The fact that it is a smartwatch and it uses a rechargeable battery means that the battery will wear out over time, so you won't be able to use it forever (few years) unless there is a option to replace the battery.
- It runs with a software. And sooner or later, Garmin will probably stop to roll out updates and it will become outdated
2. Usage: Eventho I am a active person (I go runnning, climbing, hiking, travelling, etc) and a lot outdoors, my watch (with normal glass) has nearly no scratches. Just because there isn't a lot that is hard and strong enough that gets close enough to my wrist to scratch it. You really have to expose it to a lot, to damage it a lot.

So I think, sapphire-glass watches are only usefull on "normal" watches that still work decades later and don't get outdated very fast. Any smartwatch will probably be obsolete in a few years.

That is just my opinion and thoughts about it, others my think different. And also: The things that I am saying are not 100% facts, that are just my observations and experiences. Again, others my think differently.