Polar Grit X2 vs Amazfit T-Rex Ultra 2: ECG or 30-Day Battery?

The Polar Grit X2 and the Amazfit T-Rex Ultra 2 both market themselves as rugged outdoor watches, but they’re aimed at very different wrists. One leans into training depth and a lighter feel. The other leans into raw endurance, smart features, and pure survivability. Picking the right one comes down to whether you train more than you trek, or trek more than you train.

Key Differences

• Battery life: Amazfit lasts 30 days in smartwatch mode versus 7 days on the Polar — over 4x longer.
• Weight: Polar is 62g; Amazfit is 89.2g. That’s a 27g gap you feel on long runs.
• ECG: Only the Polar Grit X2 offers ECG. Amazfit skips it.
• NFC payments: Amazfit has it. Polar does not.
• Mic and speaker: Amazfit lets you take calls on the wrist. Polar doesn’t.
• Water rating: Amazfit at 10 ATM; Polar at 5 ATM.
• Display size: Amazfit’s 1.5-inch AMOLED is larger than Polar’s 1.28-inch AMOLED.
• Launch price: Polar at $499, Amazfit at $549.

Deep Dive Comparison

Design & Comfort

The Polar Grit X2 wears small for a rugged watch — 46mm case, 62g, reinforced polymer body with a stainless steel bezel and sapphire crystal. It’s the kind of watch you can wear on a marathon without your forearm getting tired. The Amazfit T-Rex Ultra 2 goes the other direction: 51mm, 89.2g, Grade 5 titanium bezel and back panel, fiber-reinforced polymer body. It looks and feels like a tool watch. If you have a smaller wrist or hate bulk during workouts, the Polar wins this round by a wide margin. If you want something that takes a hit on a rocky trail and shrugs it off, the Amazfit is built for that abuse.

Battery Life

This is the biggest gap in the whole comparison. The Polar Grit X2 delivers 168 hours (7 days) in smartwatch mode and 30 hours of multi-band GPS. That’s solid. The Amazfit T-Rex Ultra 2 delivers 720 hours (30 days) in smartwatch mode and 50 hours of multi-band GPS. That’s borderline absurd. For a thru-hike, an expedition, or anyone tired of charging on a Tuesday night, the Amazfit isn’t just better — it’s a different category.

Health & Fitness Features

The Polar Grit X2 carries Polar’s signature training science — Gen 4 optical HR, ECG, SpO2, skin temperature, barometer, magnetometer, and multi-band GPS. ECG is the headline differentiator: you get on-demand heart rhythm readings the Amazfit can’t match. The Amazfit T-Rex Ultra 2 uses the BioTracker 6.0 PPG sensor with accelerometer, gyroscope, barometer, ambient light, and temperature, plus multi-band GPS. It tracks heart rate and activity well, but there’s no ECG and no SpO2 listed in its sensor stack. If you want clinical-leaning metrics and serious training analysis, Polar wins. If you want general wellness with rugged tracking, Amazfit holds its own.

Smart Features

This is where the Amazfit pulls ahead. NFC contactless payments, a mic and speaker for Bluetooth calls, Wi-Fi 2.4GHz, Bluetooth 5.2, and 64GB of storage make it the more modern smartwatch of the two. The Polar Grit X2 sticks to Bluetooth and ANT+, no NFC, no mic, no speaker. Polar’s strength has always been training, not lifestyle. If paying at the coffee shop or taking a call mid-walk matters to you, the Amazfit is the only option here.

Price & Value

At launch, the Polar Grit X2 ran $499 and the Amazfit T-Rex Ultra 2 lists at $549. That’s a $50 gap in Amazfit’s favor for what is — feature for feature — the more loaded watch. You’re paying for Polar’s training ecosystem and ECG, not raw hardware. For pure spec value, Amazfit wins. For training tools and software, Polar still earns the premium.

Technical Specs

Spec	Polar Grit X2	Amazfit T-Rex Ultra 2
Launch Price	$499	$549
Case Size	46mm	51mm
Weight	62g	89.2g
Case Material	Reinforced polymer, stainless steel bezel, sapphire crystal	Fiber-reinforced polymer, Grade 5 titanium bezel and back
Water Rating	5 ATM	10 ATM
Display	1.28-inch AMOLED, 416 x 416	1.5-inch AMOLED, 480 x 480
Smartwatch Battery	168 hours (7 days)	720 hours (30 days)
GPS Battery	30 hours	50 hours
GPS	Multi-band	Multi-band
Connectivity	Bluetooth, ANT+	Bluetooth 5.2, Wi-Fi 2.4GHz, NFC
NFC Payments	No	Yes
Mic/Speaker	No	Yes
Storage	32GB	64GB
Sensors	HR, ECG, SpO2, Skin Temp, Barometer, Magnetometer, Accelerometer, Ambient Light	BioTracker 6.0 PPG, Accelerometer, Gyroscope, Barometer, Ambient Light, Temperature

The Verdict

Buy the Polar Grit X2 if you’re a runner, cyclist, or triathlete who actually trains, wants ECG and Polar’s recovery and load analytics, and prefers a lighter watch you can wear all day without noticing it. The 62g build and sapphire crystal make it the smarter pick for athletes putting in serious volume.

Buy the Amazfit T-Rex Ultra 2 if you want a watch that lasts a full month between charges, survives anything you throw at it, and gives you NFC payments and on-wrist calls without compromise. For thru-hikers, expedition users, and anyone sick of charging cables, this is the watch.

Different watches for different lives. The Polar is the athlete’s tool. The Amazfit is the adventurer’s tank.

Frequently Asked Questions

Which watch is better overall, the Polar Grit X2 or the Amazfit T-Rex Ultra 2?

It depends on your use case, but the Amazfit T-Rex Ultra 2 is the better value on paper — more battery, more smart features, better water rating, larger display, all for $50 more. The Polar Grit X2 is the better training watch thanks to ECG and Polar’s coaching ecosystem.

Does the Amazfit T-Rex Ultra 2 have ECG like the Polar Grit X2?

No. ECG is exclusive to the Polar Grit X2 in this matchup. If on-demand heart rhythm readings matter to you, Polar is your only option here.

Is the Amazfit T-Rex Ultra 2 worth $50 more than the Polar Grit X2?

For most outdoor and adventure users, yes — you’re getting 23 extra days of smartwatch battery, NFC payments, a mic and speaker, double the storage, and a stronger 10 ATM water rating. For dedicated runners and triathletes, Polar’s training tools still justify the cheaper price tag.

Which watch is better for serious runners and triathletes?

The Polar Grit X2. It’s 27g lighter, has ECG and SpO2, and runs on Polar Flow — one of the most respected training platforms in endurance sports. The Amazfit is more rugged but isn’t built around the same depth of training analysis.

Do both watches work with iPhone and Android?

Yes, both pair via Bluetooth with iPhone and Android. The Amazfit T-Rex Ultra 2 adds Wi-Fi and NFC for tap-to-pay, which only works on the Amazfit side regardless of phone platform.