Garmin vs Whoop vs Oura vs Apple Watch vs Fitbit: Hardware & Software Differences Explained (2025)
- Ryan - Kygo Health
- Mar 6
- 6 min read
Updated: Mar 22
Last Updated: March 6, 2026
Every wearable promises to track your heart rate, sleep, stress, and recovery. But the hardware and software differences between Garmin, Whoop, Oura, Apple Watch, and Fitbit are bigger than most people realize — and in some cases, devices aren't measuring at all. They're estimating.
We broke down the exact hardware inside each device, mapped it to the health metrics it produces, and separated what's actually measured from what's purely software. Here's what makes each one different.
The Hardware Differences Are Bigger Than You'd Think
The Apple Watch Ultra 3 packs 11 distinct health sensors. The Oura Ring 4 has 4. That's not a quality judgment — it's a form factor trade-off. A ring can't fit a GPS chip, gyroscope, or barometric altimeter.
But sensor count alone doesn't tell the full story. Oura's 4 sensors include an 18-path PPG system with 3 photodiodes reading through finger arteries — where the blood signal is stronger and motion noise is lower than the wrist. That design gives Oura 120% better signal quality than its previous generation, according to Oura's own data.
Meanwhile, Whoop 5.0 also has just 4 sensors, but its PPG samples at 26 Hz — the fastest of any device here. That higher sampling rate matters most during exercise, where rapid heart rate changes need more data points to track accurately.
Garmin sits at 10 sensors with the Venu 4, including the best GPS in the group (multi-band GNSS with L1/L5 dual-frequency). Fitbit Charge 6 comes in at 7 sensors but holds a unique card: it's the only device here with an EDA (electrodermal activity) sensor for measuring stress through skin conductance.
Hardware Differences: What's Actually Inside Each Device
All six devices share the basics — optical heart rate (PPG), SpO2, accelerometer, and skin temperature. The differences start at ECG, GPS, and the specialized sensors.
Feature | Garmin Venu 4 | Whoop 5.0 | Oura Ring 4 | Apple Watch S10 | Apple Watch Ultra 3 | Fitbit Charge 6 |
Total Sensors | 10 | 4 | 4 | 10 | 11 | 7 |
ECG | ✓ | MG only | ✗ | ✓ | ✓ | ✓ |
GPS | Multi-band | ✗ | ✗ | L1 | L1/L5 | Connected |
Gyroscope | ✓ | ✗ | ✗ | ✓ | ✓ | ✗ |
EDA (Stress) | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ |
Depth Gauge | ✗ | ✗ | ✗ | 6m | 40m | ✗ |
Four of the six devices have single-lead ECG for atrial fibrillation detection: Garmin Venu 4, Apple Watch S10, Apple Watch Ultra 3, and Fitbit Charge 6. Whoop only offers ECG on the separate Whoop MG model. Oura has no ECG hardware at all.
Only Garmin and both Apple Watches include a gyroscope — which matters for fall detection. Whoop, Oura, and Fitbit can't offer fall detection without this sensor.
For the full interactive sensor-by-sensor breakdown, see our Wearable Hardware & Software Comparison Tool.
How Hardware Differences Affect What You Actually Get
The same metric name on two devices doesn't always mean the same measurement quality.
Heart Rate Variability (HRV)
All six devices track HRV using PPG. But Oura reads HRV from finger arteries where the pulse signal is cleaner, producing both nighttime and daytime HRV measurements. Most wrist-based devices only report nightly HRV averages because daytime wrist motion creates too much noise.
Sleep Apnea Detection
Sleep apnea detection is Apple Watch-only — and it doesn't use SpO2. Instead, it relies on the accelerometer to detect tiny wrist micro-movements caused by interrupted breathing. The algorithm needs 30 nights of data before it can assess your breathing disturbance levels. Apple reports 89% sensitivity for severe sleep apnea and 43% for moderate, and the feature has FDA authorization.
Stress Measurement
Fitbit measures stress directly using its EDA sensor — a direct sympathetic nervous system signal. Garmin, Whoop, and Oura all estimate stress indirectly from HRV patterns. Both approaches have value, but they're measuring fundamentally different things. Apple Watch has no stress feature at all.
Hypertension Alerts
Hypertension alerts are exclusive to Apple Watch Ultra 3. The feature uses PPG pulse wave analysis to flag hypertension trends over 30-day periods. Apple trained the algorithm on over 100,000 participants.
Software Differences: Where Brands Really Diverge
Strip away the hardware, and you find the widest differences in proprietary software algorithms. These features all run on the same raw sensor data — what changes is how each brand interprets that data.
Brand | # Algorithms | Key Proprietary Features |
Whoop | 8 | Recovery Score, Strain Score, VO2 Max, Healthspan, AI Coach (OpenAI) |
Garmin | 6 | Body Battery, Health Status, Firstbeat Analytics |
Oura | 4 | Readiness Score, Cardiovascular Age, Resilience |
Apple | 4 | Vitals App, Hearing Health |
Fitbit | 3 | Stress Management Score (EDA + HRV + RHR + Sleep) |
Whoop leads with 8 proprietary algorithms, including Recovery Score, Strain Score, VO2 Max (added in 2025), Healthspan/biological age estimation (built with the Buck Institute), Journal behavior tracking for 160+ habits, and an AI Coach powered by OpenAI that answers natural-language health questions.
Garmin follows with 6 algorithms built on Firstbeat Analytics, headlined by Body Battery — the only real-time energy score that updates throughout the day as you rest or exert yourself. They also added Health Status on the Venu 4, which integrates 5 health metrics into a single daily view.
Oura offers 4 algorithms focused on sleep and recovery, including Cardiovascular Age and a Resilience score that tracks stress-recovery patterns over weeks.
Apple has 4 features including the Vitals App (overnight health dashboard with out-of-range alerts) and Hearing Health (the only wearable monitoring environmental noise exposure).
Fitbit's 3 algorithms include the most detailed stress breakdown: the Stress Management Score combines EDA data, HRV, resting heart rate, sleep, and activity into three sub-scores — Responsiveness (30 points), Exertion Balance (40 points), and Sleep Patterns (30 points).
FDA-Cleared Medical Features by Device
Not all health features carry the same regulatory weight. Here's what actually has FDA clearance or authorization:
Device | FDA Features | Details |
Apple Watch Ultra 3 | 3 | ECG/AFib, Sleep apnea, Hypertension alerts |
Apple Watch S10 | 2 | ECG/AFib, Sleep apnea |
Garmin / Fitbit | 1 each | ECG/AFib detection |
Whoop / Oura | 0 | No FDA-cleared features on standard models |
One Important Note: Apple Watch SpO2 in the US
Apple Watch blood oxygen measurement was disabled on US models from January 2024 due to a Masimo patent ruling. Apple re-enabled the feature in August 2025 via a workaround — the watch captures raw data, but processing happens on the paired iPhone rather than on-device. Masimo is legally contesting this workaround. The feature works without restriction outside the US.
How Kygo Connects It All
Each of these devices generates valuable health data — but they all live in separate apps with different scoring systems and terminology. That's the core problem Kygo solves.
Kygo connects to your wearable (Oura, Apple Watch, Garmin, Fitbit, or Whoop) and combines your biometric data with nutrition tracking in one unified dashboard. You can see how what you eat affects your HRV, sleep quality, recovery scores, and more — regardless of which device you wear.
No matter which hardware you choose from this comparison, Kygo gives you a single place to understand all of it.
Which Device Should You Pick?
There's no single best device — it depends on what you care about most.
If recovery-focused training is your priority, Whoop's strain-to-recovery system is purpose-built for athletes. If sleep quality and passive 24/7 tracking matter most, Oura's finger-based PPG gives the cleanest biometric signal. If you want the most sensors and FDA medical features in one package, Apple Watch Ultra 3 is the clear hardware leader. If GPS accuracy and outdoor fitness metrics are your focus, Garmin Venu 4 has the best satellite receiver in the group. And if stress measurement through dedicated hardware (not just HRV estimation) matters to you, Fitbit Charge 6 is the only option with EDA.
Priority | Best Pick | Why |
Recovery training | Whoop 5.0 | Strain-to-recovery system for athletes |
Sleep & passive tracking | Oura Ring 4 | Cleanest finger-based PPG signal |
Max sensors & FDA | Apple Watch Ultra 3 | 11 sensors, 3 FDA features |
GPS & outdoor | Garmin Venu 4 | Multi-band GNSS L1/L5 |
Stress hardware | Fitbit Charge 6 | Only EDA sensor |
Explore the full interactive comparison in our Wearable Hardware & Software Comparison Tool — compare sensor hardware, health metrics, and software algorithms across all 6 devices.
Sources
This post is for informational purposes only and is not medical advice. Always consult a healthcare professional for medical decisions. Kygo Health does not diagnose, treat, or cure any medical condition.