Fitbit IonicGarmin Vivoactive 3
Tech specs 
SizeWatch Width: 38mm
Watch Thickness: 12mm
43.4 x 43.4 x 11.7 mm
Material- Strong & lightweight 6000 series aerospace-grade aluminum.
- The wristband is made of a flexible, durable elastomer material
Case material: fiber-reinforced polymer and stainless steel
Lens material: Corning® Gorilla® Glass 3
Bezel material: stainless steel
ChargingUSBUSB
BatteryLithium-polymerRechargeable lithium-ion
Battery life4+ days with a GPS battery life up to 10 hours (1-2 hours charge time)GPS mode: Up to 13 hours
Smartwatch mode: Up to 7 days
Water-resistanceup to 50 metres (swim-proof) - 5 ATM5 ATM
Weight50 grams43 g
SensorAltimeter, 3-axis accelerometers, digital compass, GPS, optical heart rate monitor, ambient light sensor, sensors & components, vibration motor.GPS, barometric altimeter, compass, accelerometer, thermometer, heart rate
DisplayHi-res touchscreen (up to 1000 nits). Corning Gorilla Glass 3 display.sunlight-visible, transflective memory-in-pixel (MIP), 240 x 240 pixels
Screen size29 x 21mm, 348 by 250 pixels1.2" (30.4mm) diameter
ColorsComes is Sport, Leather and Classic versions.Black, White
Other- Saves 7 days of detailed motion data – minute by minute.
- Saves daily totals for past 30 days
PLATFORM: Home Grown OS
PROCESSOR: Unknown
MEMORY: 7 timed activities, 14 days of activity tracking data
CONNECTIVITY: WiFi, Bluetooth
Activity tracking 
StepsYesYes
DistanceYesYes
Calories burnedYesYes
ActivityYesYes
FloorsYesYes
SleepYes (light, deep & REM)Yes
Heart rateYes (Stores heart rate data at 1 second intervals during exercise tracking and at 5 second intervals all other times)Yes
Stress & recoveryYes
UV exposure
Skin temperature
Galvanic skin response
Hydration level
Calorie intake
GPSGPS/GLONASSYes
Running featuresPace, distance & routesPreloaded running profiles, GPS based distance/time/pace, run workouts, foot pod capable
Swimming featuresLap count, duration & calorie burnPreloaded swim profiles; Pool swim metrics (lengths, distance, pace, stroke count/rate, calories); Stroke type detection (freestyle, backstroke, breaststroke, butterfly); Pool swim workouts
Swim efficiency (SWOLF)
Other - SpO2 sensor that measures blood oxygen levels
- Guided breathing sessions
- Female health tracking
- gym workout tracking
- music control, find my phone, etc..
- Built in apps for running, golfing, cycling, swimming, snowboarding/skiing, paddle board, rowing, cardio, walking, strength training, rep counting, yoga, eliptical, stair-stepper and more.
Non-fitness functions 
Smartphone notificationsCall, text and calendar notificationsYes
On-board music storageYes, 2.5GB (300 songs) + access Pandora
Connected payYesYes
LTE
Links 
Affiliate link*Amazon | FitbitAmazon
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