It seems to be a great deal of debate with regards to wear or durability on these things:
Firstly, I have had mine since January, I replaced it once as the screen cracked within 3 days of me owning it, just developed a crack, so took it back and got it replaced. Never a good start I know. Mine came from earlier stock.
But I use mine every day, to ride, in the gym, i use weights. Its got no dents, the screen is immaculate, the clasp has minor scratches, no tears, the band is a little scuffed cos its made out of some kind of silicon rubber, but otherwise it has been used every day with 0 issues in an active environment. That includes Chest press, inclines, squats, dead lifts etc.
The only time I take it off is when I am doing tricep dips, because it puts so much pressure on your wrists. I do not take it off for anything else though. I wear mine on the inside of my wrist. I am as active as anyone, and I find it very useful. You need to be aware of what your doing before you do it mind you, that has basically been my guide. If your going to be using it like I do, just simply exercise a little common sense. if your going to be putting a lot pressure on your wrist, maybe take it off.
People say the others are more durable, I would view that with caution, I see guys taking them off, apple watch for example might be waterproof, but i see peeps still take them off in the gym. They are not that durable either, I see them get scratched just as easy. I cant comment on the fitbits, but there screens are not the same anyway, the rest are lcd displays, and they are just as delicate.
Common sense and ive had 0 issues since January, just dont drop it, its top heavy, and will smash the screen. No screen protector will save you. Buy a cheap one to start, theyre no more durable than the expensive ones, but it will allow you to try one out for like ?20. The glassless ones are just bands, different thing altogether.