My wife was using a Fitbit Charge HR for a while. After the novelty wore off, it seemed like a bit of a hassle to have to charge it up every few days. Her daughter has it now.

I have a Garmin vivofit 2. https://buy.garmin.com/en-US/US/into-sports/health-fitness/vivofit-2/prod504038.html It's about $50 cheaper and has a few less features (no heart rate monitoring, no vibration alarm for calls/texts etc) but uses watch batteries so the time for replacement is about 6 months instead of charging it every few days. It's also water proof so you can leave it on all the time if you like.

I think the Garmin is less hassle because of the battery life and being water proof because if you have something that's a hassle to use while you're trying to get healthy, that will become an excuse at some point to not continue with it. 

What was/is most helpful to me is having the tracker associated with a www.myfitnesspal.com account.  If a person is looking to lose weight you have to consistently and honestly track your calorie intake.  You can spend all your free time walking, but that isn't gonna burn off 3 helpings of hotdish at supper time.  The activity tracker alone won't make you healthier but for some, having a "wrist reminder" is a good way to keep you motivated and on track.