The Ultra's Sapphire glass should scratch less than your series 4 (unless you are using a n S4 with sapphire glass already)

But, it is more prone to shattering. The raised lip and flat glass helps with this, and the speakers are much bigger, too. Don't know if the Microphone would hold up though, I don't work where my watch is exposed to fine metal particles. Guess I should consider myself lucky lol