When comparing Garmin Vivosmart vs Garmin Vivofit 3, the Slant community recommends Garmin Vivofit 3 for most people. In the question“What are the best fitness trackers?” Garmin Vivofit 3 is ranked 24th while Garmin Vivosmart is ranked 25th. The most important reason people chose Garmin Vivofit 3 is:
The Vivofit 3 is waterproof up to 50 meters. You can confidently take it swimming, or wear it in the shower without risk of damaging the tracker.
Specs
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Pros

Pro Smartwatch-like functionality
Vivosmart is capable of showing smartphone notifications and control music playback.
Pro Logs exercise
Pro Week's battery life
Pro Some customization options
Pro Displays time
Pro Good step counter
Pro Completely safe for swimming and showering
The Vivofit 3 is waterproof up to 50 meters. You can confidently take it swimming, or wear it in the shower without risk of damaging the tracker.
Pro No need to recharge the tracker
The Vivofit 3 runs on battery so there is no need to worry about keeping it charged.
With a battery life of up to 1 year, it can go longer without a battery change than most other fitness trackers.
Cons
Con Companion app is difficult to use
The way the information is presented is confusing and incoherent and there's no logical way to find necessary information.
Con No activity autodetection
Vivosmart does not automatically detect when you start to walk or run, you have to start and stop activity manually.
Con Reps counting feature does not work for some exercises
Reps counting feature is not reliable, sometimes it misses few reps and with some exercises it can count 1 rap, even if you did 10 reps for example. And it can't detect when you start the exercise, so you have to start and stop the counter manually. In practice I frequently forget to start and to stop the counter so after some time I simply sopped using this feature.
Con Difficult to check current time because display most of the time is turned off
In order to turn on the display, for example to see current time, you need to raise you hand and after some delay display some times turns on, sometimes not.
Other option is to double tap the display, which requires both hands.
If you frequently checking current time, it is really annoying.
Con App requires you to provide personal data in order to work
You have to register in the app providing information about your age, gender and weight.
Con App does not work without internet connectivity
It is not possible for example to enter your weight if you are not connected to the internet.
Con No GPS data is collected
Con Too unreliable for the cost
The Vivofit 3 has multiple serious issues impacting its reliability which means you're taking a gamble by purchasing it. At $80, you can get trackers with much better build qualities and a similar set of features.
Con Software that detects different activity often doesn't work
The "Move IQ" software in the tracker, which is supposed to detect different types of exercise, often doesn't work. Either it will track everything as walking, or will not start tracking them all.
Con It's easy to lose the watch because of the weak clasp
The clasp frequently comes undone during physical activity because of its poor design. If you aren't constantly paying attention to it or add re-enforcement to the clip, it would be easy to lose the tracker.
Con Syncs with a limited number of devices
Con Not for people with small wrists
The tracker is available in two sizes, regular or extra large. The regular band is too long for people with below average sized wrists.
