No you should not because besides the same aluminum the iPhone has the same Gorilla glass. Apple is working on an iPhone for daily use and it should be out soon.😀
THE APPLE WATCH WILL BE ON YOUR HAND AND MOST PEOPLE WEAR LONG SLEEVES AND THEIR HAND IS ENCOUNTERED WITH MANY OTHER THINGS (I knwo how it sounds🙂)
iPhones are in the pocket but as you saw on the picture they could be scratched really easy without a case.
Your Watch will encouter many things. I don't know about you but I have worn watches for years and only worn with saphire glass and steel or titanium case.
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They're using a stronger Aluminum for Apple Watch Sport than they used for the iPhones. They even called out how this is a new, stronger Aluminum that will set the standard for their future aluminum use.
Yeah, I know. It's a guess. But since there are many people considering Sport version because of the price I just want you to know the probable risk.