You're probably better off with a cheap Garmin for that. The battery will last a month instead of a day. (Or multiple months if you only wear it at night and turn it off every morning)
That would be a reasonable answer most of the time, but as the topic was sleep tracking I'd disagree. Consensus I've seen seems to be that Apple has better sleep tracking (having used both, I would agree). Even if they don't, one can swap out to use another sleep tracking app. I think you're stuck with what you get out of the box with Garmin. (Though I've not looked at Garmin's app store. Knowing what I do about their SDK, I doubt a 3rd party could write a usable replacement app.)
That would be a reasonable answer most of the time, but as the topic was sleep tracking I'd disagree. Consensus I've seen seems to be that Apple has better sleep tracking (having used both, I would agree). Even if they don't, one can swap out to use another sleep tracking app. I think you're stuck with what you get out of the box with Garmin. (Though I've not looked at Garmin's app store. Knowing what I do about their SDK, I doubt a 3rd party could write a usable replacement app.)