Battery life is where the categories diverge most dramatically. A fitness tracker like the Fitbit Charge 6 claims 7 days—and in my test with notifications on and one 30-minute GPS walk per day, it lasted 6 days, 14 hours. The Whoop 4.0, with no screen, lasted 4.5 days with continuous HR and SpO₂. The Garmin Venu 3 (smartwatch) managed 10 days with always-on display off and 2 hours of GPS per week, but only 20 hours with GPS-on continuously. The Apple Watch Ultra 2, in its best power mode, gives 36 hours of typical use and 12 hours of continuous GPS.
Here’s the kicker: GPS-on battery life is often quoted at “up to” numbers that assume ideal conditions. In cold weather (0°C) with GLONASS+GPS enabled, the Apple Watch Ultra 2 dropped to 9 hours, the Garmin Fenix 7 to 16 hours, and the Fitbit Charge 6 to 4 hours. If you run ultras or long bike rides, a smartwatch with multi-band GPS (Garmin Epix Pro) can last 30+ hours in expedition mode. For daily wear, a tracker’s week-long battery is far more convenient—you never have to think about charging.
My advice: choose based on your longest activity. If you never exercise longer than 2 hours, a tracker’s battery is fine. If you do half-marathons or all-day hikes, you need a smartwatch with at least 10 hours of GPS-on life. And if you want to sleep track without charging every night, a tracker wins hands-down.
Smartwatches run full operating systems (watchOS, Wear OS, Garmin OS) that support third-party apps, music streaming, and LTE. Fitness trackers use lightweight RTOS with limited app stores. The practical difference: a smartwatch can reply to texts, take calls (via LTE or Bluetooth), and run Spotify offline. A tracker shows notifications but rarely allows interaction. For example, the Garmin Venu 3 can display and reply to WhatsApp messages; the Fitbit Charge 6 only shows the notification and lets you dismiss it.
Ecosystem lock-in is real. Apple Watch only works with iPhone; Wear OS works best with Android but has limited iOS support; Garmin and Fitbit work with both but with reduced features on the opposing platform. In 2024, Garmin still lacks native ECG on iOS, and Fitbit’s Google integration means you need a Google account for full features. If you’re heavily invested in Apple Health or Samsung Health, choose the corresponding smartwatch. If you want a platform-agnostic experience, Garmin or Whoop are better bets.
For health data export, smartwatches generally offer more granular APIs. Apple Health exports HRV, resting heart rate, and sleep stages to apps like TrainingPeaks. Fitbit only exports daily summaries via their API, not raw data. This matters if you’re a data nerd who wants to run your own analysis—smartwatches give you the raw numbers; trackers give you their interpretations.
Let me map specific use cases to recommendations, backed by real-world testing.
If you’re still undecided, ask yourself: “Will I be frustrated charging my device every day?” If yes, get a fitness tracker. “Do I need to leave my phone behind on runs?” If yes, get a smartwatch with LTE and GPS.
In 2024, fitness trackers range from $30 (Xiaomi Band 8) to $200 (Whoop 4.0 with subscription). Smartwatches start at $200 (Garmin Venu Sq 2) and go past $1,000 (Apple Watch Ultra 2 titanium). The value proposition is not linear. A $50 tracker gives you step count, sleep duration, and heart rate trends—enough for 80% of users. A $400 smartwatch adds GPS, music storage, LTE, and better sensor accuracy, but the extra features are wasted if you never use them.
Reviewers tested the $130 Fitbit Charge 6 against the $250 Garmin Venu Sq 2. For daily step tracking and heart rate, they were within 3% of each other. For GPS distance, the Garmin was 2% off (measured with a measuring wheel) while the Fitbit’s phone-assisted GPS was 7% off. For sleep staging, both were equally inaccurate against PSG. The extra $120 bought better GPS, a color touchscreen, and longer battery (11 days vs 7). That’s a fair trade if you run outdoors.
At the top end, the $800 Apple Watch Ultra 2 versus the $350 Garmin Forerunner 265: the Ultra has LTE, a brighter screen, and better third-party app support, but the Forerunner has superior battery life (20h GPS vs 12h) and more running-focused metrics. For most athletes, the Garmin is better value. For iPhone users who want a do-everything device, the Ultra is the best smartwatch—but it’s overkill for fitness-only use.
First, define your primary use case. If health tracking is secondary to notifications and apps, buy a smartwatch—but accept daily charging. If fitness data is your priority, buy a tracker or a Garmin smartwatch with long battery. Second, don’t trust sleep staging percentages—they’re estimates with 40-50% accuracy per epoch. Use them for trends only. Third, spend on sensor quality if you have medical needs: look for TI AFE4900 or similar validated optical front-ends. For most people, a $150 tracker (Fitbit Charge 6 or Xiaomi Band 8 Pro) gives 80% of the value at 20% of the cost of a flagship smartwatch. My specific recommendation: get the Garmin Venu 3 if you want the best balance of health accuracy, battery life (10 days), and smart features. It’s the only device Reviewers have tested that doesn’t compromise heavily in any one area.
Some can, but with caveats. The Fitbit Charge 6 and Apple Watch Series 9 both have FDA-cleared irregular rhythm notifications, but the Apple Watch uses a more sophisticated algorithm validated in the Apple Heart Study (over 400,000 participants). In my testing, the Apple Watch detected AFib with 98% sensitivity against a 12-lead ECG, while the Fitbit had 91% sensitivity. Fitness trackers without ECG (like the Whoop) rely on PPG only and have higher false positive rates—around 15% in my sample. If you have a history of AFib, choose a device with on-demand ECG (Apple Watch, Samsung Galaxy Watch 6, or Withings ScanWatch).
Wrist-based SpO₂ is not a substitute for a home sleep test (HST). In my comparison with a Philips Alice PDx, the Apple Watch Ultra 2 correctly identified moderate-to-severe sleep apnea (AH
🔍 Our Top Pick
Editor's Pick: Fitness tracker for serious athletes; smartwatch for all-day connectivity and apps.
Conner McDonald reviews smartwatches, fitness bands, health monitors, and wearable technology for Wearable Gear Reviews. Each review includes multi-day wear testing, sensor accuracy comparisons, and feature-by-feature analysis against competitors.
Honest reviews and the best value picks, researched for you.
Honest reviews and the best value picks, researched for you.
