When comparing Fitbit Surge vs Polar M400, the Slant community recommends Polar M400 for most people. In the question“What are the best fitness trackers that pair with iPhones?” Polar M400 is ranked 2nd while Fitbit Surge is ranked 18th. The most important reason people chose Polar M400 is:
The "Sport Profile" feature allows you to customize what stats you want to see for each type of exercise. For example, you may want the GPS on for running but not for a circuit workout. These preset profiles save you from having to set up the device each time you exercise.
Specs
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Pros
Pro Continuous heart rate tracking eliminates risk of forgetting to activate the feature
The Fitbit Surge fitness tracker has automatic, continuous, wrist based heart rate tracking. Heart rate data is stored at one second intervals during exercise, and at five second intervals during non-exercise activities.
Pro LCD screen that can display multiple stats without the need of using the app
Similar fitness trackers depend on Bluetooth in order to relay info to a smartphone. Fitbit Surge can display information locally on the display which is far more convenient.

Pro Lets users log meals by voice
Users can tell Surge what was eaten, and a database will be used to match the entry with nutritional information.
Pro Does not need to be recharged frequently
The battery lasts 5-7 days which is one of the longer lasting options for rechargeable fitness trackers.

Pro Easy to operate compared to display-less options
While Surge easily syncs with iOS, Android, and Windows phones, it does not depend on them for functionality. The touch screen and physical buttons are a huge step up from display-less models.
Pro Gives you a lot of options for customizing different types of workouts
The "Sport Profile" feature allows you to customize what stats you want to see for each type of exercise. For example, you may want the GPS on for running but not for a circuit workout. These preset profiles save you from having to set up the device each time you exercise.
Pro Gives you custom activity goals suitable for your level
The daily activity goal is a good way to find out how active you really are in your everyday life. Here you can choose your typical activity level from three options and see how active you need to be to reach your daily activity goal.
The time you need to complete your daily activity goal depends on the level you have chosen and the intensity of your activities. Age and gender also affect the intensity you need to reach your daily activity goal.
Pro Detailed reports
The fitness tracker offers excellent reporting including distance, speed, cadence, heart rate (if paired with monitor), ascent, decent, calories, recovery status, and more.
Pro Ability to add training notes
The app allows you to add additional notes to your workouts for better tracking.
Cons
Con Might cause skin irritation for some
A number of people are reporting the Surge causes skin irritation. According to the company it's a very small percentage of customers.
Con Screen prone to inadvertent touches
It's really easy to accidentally brush up against the fitness tracker's watch and end up on screens that the user wasn't intending to navigate to. This forces you to swipe back to the correct screen.
Con Fairly big investment
While it's one of the most advanced trackers that Fitbit offers, it comes with a hefty price tag.
Con Sleep tracking lacks detail and accuracy
If you are awake for an extended period of time in the middle of the night and then fall back asleep, the fitness tracker may not see the additional hours as part of your sleep.
Con Unattractive and bulky design
The tracker is quite wide and hard to miss, it's not something that can blend in with what you're wearing outside of sport/exercise type settings.
Con Short battery life when using the GPS
With the GPS turned on, battery life goes from around 24 days to 9 hours.
This is likely fine for people who will always have opportunities to charge it after their run. However for anyone hoping to use the GPS for longer activities, such as hiking, that may not be long enough to be useful.
