What does "GMT" mean on watch models, and how useful is it?

[Participant]

Trying to decide between two similar models, one of which is "chronograph" and one of which is "GMT", that doesn't have the chronograph functions.

What does GMT add to a watch and is it worth it? Also what do they mean when they refer to "sapphire"?

 

[JKD]

GMT shows you the time in a second time zone with an extra hour hand. Sapphire is the crystal (glass) - means it's very hard to scratch. Mineral crystal is cheaper and easier to scratch.

I personally prefer GMT watches to chronographs - but that's just me. I think most prefer chronographs for the cool factor - and some badly designed GMT watches are hard to read at a glance.