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Garmin vs. Polar vs. COROS: Which Running Watch?

Garmin vs. Polar vs. COROS: Which Running Watch?

Garmin vs. Polar vs. COROS: Which Running Watch for Marathon Training?

Standing in a running specialty store, staring at three nearly identical GPS watches with wildly different price tags, you might wonder which brand deserves your training budget. Garmin, Polar, and COROS all occupy different positions in the running watch market, with COROS generally positioning itself as a more budget-friendly option, with most watches falling in the $200-$700 range</cite>, while Garmin running watches range in price from around $150 to over $1,200</cite>. Polar sits somewhere in between, focusing heavily on heart rate accuracy and recovery metrics.

All three brands build reliable GPS watches that can track your marathon training. The real differences emerge when you examine what each brand does best and where they make compromises.

What Garmin Does Best

Garmin owns the largest market share for good reason. The company produces an enormous range of watches, from the Forerunner 55, which delivers rock-solid GPS, wrist-based heart rate, daily suggested workouts, and recovery time at $150, to flagship models costing well over $800.

Garmin continues to dominate when it comes to accuracy, training depth, and ecosystem strength. The Garmin Connect app stands out as the most comprehensive training platform among the three brands. You get detailed analytics, training status indicators, suggested workouts that adapt to your fitness level, and Garmin Coach, which offers free adaptive training plans available in the app for 5K, 10K, or half marathon distances.

The mid-range models like the Forerunner 265 offer Garmin's brightest and sharpest AMOLED touchscreen display yet, plus training status, training readiness and performance condition features. Battery life ranges from 19 hours of GPS runtime on the Forerunner 165 to 26 hours on the Forerunner 255, with smartwatch mode lasting days to weeks depending on the model.

For marathon runners, Garmin watches excel at pacing strategy. PacePro is Garmin's built-in pacing tool that's useful for hilly marathons like Boston, creating a pacing plan that takes into account the amount of uphill or downhill in each mile or kilometer split.

Inline image showing Garmin watch interface displaying training metrics during a run

Where Polar Shines

Pioneers of heart rate tracking, Polar still makes some of the very best heart rate monitors going. The Finnish company built its reputation on cardiac monitoring accuracy, and that heritage shows in every watch they produce.

The Polar Vantage series and newer models like the Grit X2, which features a slimmer profile, lighter weight, and a 1.28-inch AMOLED display protected by sapphire crystal</cite>, deliver professional-grade biosensing. These watches feature 4th-generation optical heart-rate tracking, wrist-based ECG, SpO₂ sensing and skin temperature tracking.

Polar's training philosophy centers on recovery and readiness. The Nightly Recharge, Training Load Pro and Orthostatic Test help you understand how your body is adapting, when to train hard and when to rest. This approach makes Polar watches particularly valuable for runners prone to overtraining or those balancing high training loads with demanding schedules.

The Polar Pacer Pro offers good value as a mid-range option with great GPS, even if the LCD screen is a bit bare-bones. At launch, the COROS Pace Pro was priced at $349, which is $100 cheaper than the Garmin Forerunner 265 at $449 and $50 cheaper than the Polar Vantage M3 at $399.95.

The Polar ecosystem works well for runners who want deep health insights without drowning in metrics. The interface tends toward simplicity compared to Garmin's feature-dense approach.

The COROS Value Proposition

COROS entered the GPS watch market later than its competitors but quickly earned respect among endurance athletes. The big thing that sets COROS apart from competitors is the insane battery life, a scroll button, and the willingness to constantly innovate and develop its software.

The COROS Pace 4 offers impressive features at approximately $249. In max GPS mode with all satellite systems active, the Pace 4 delivers 31 hours of battery life, and if you leave the screen set to 'always on', that figure lowers to 24 hours</cite>. These numbers dramatically exceed what you get from comparably priced Garmin or Polar models.

Inline image showing COROS watch on trail with battery life indicator

The Pace 4's range of advanced running analytics is impressive for the price. You get the same suite of Evo Lab training tools as the pricier Apex, including Running Performance, Training Load with a week overview, recovery time recommendations, running fitness scores and pace ranges</cite>.

The trade-off comes in smartwatch features. COROS watches are a bit short on smartwatch skills. Garmin does this better</cite>. COROS lacks NFC payment options, doesn't support Spotify streaming (only MP3 music storage), and offers fewer third-party app integrations.

For runners who care primarily about training data and battery endurance rather than lifestyle features, COROS delivers exceptional value. If you prioritize battery life, reliable GPS, excellent mapping, rugged durability, and handy hardware controls over a pretty screen, COROS watches are among the best performing of 2025.

GPS Accuracy and Heart Rate Performance

All three brands now offer multi-band, dual-frequency GPS on their mid-range and premium models. In testing, the dual frequency GPS on COROS watches performed well against pricier Garmin models for total distances. Real-world accuracy differences between brands have narrowed considerably.

Heart rate accuracy tells a more nuanced story. Garmin watches stress-tested against a Polar H10 heart rate monitor (the most accurate way to measure heart rate available to most people during a workout) showed accuracy within 1 beat per minute</cite> on premium models. COROS heart rate was more hit and miss during interval sessions with some big spikes, at times reading 20bpm higher than a chest strap.

Polar's optical heart rate sensors generally perform well, though no wrist-based sensor matches the accuracy of a chest strap during high-intensity intervals. For steady-state marathon pace running, all three brands deliver reliable heart rate data.

Battery Life Reality Check

Without music, a 4-hour marathon burned 21% battery on the Garmin Forerunner 165, meaning the watch easily handles race day. COROS Apex 4 offers 65 hours GPS time from the 46mm version or 41 hours from the 42mm, which exceeds most marathon runners' needs by a significant margin.

Polar lists the Grit X2 at up to 90 hours in Eco training mode, 30 hours in Performance mode, and about a week in Smartwatch mode. These figures mean you can train for an entire week, including a long run, without reaching for a charger.

Battery life matters most for ultrarunners and those who forget to charge their watches. For standard marathon training, all three brands offer sufficient endurance.

Training Features and Ecosystem

Garmin's training ecosystem remains the most comprehensive. The platform includes structured workouts, race predictors, training load tracking, recovery advice, and performance condition indicators. The data can feel overwhelming for new runners but becomes invaluable as you develop as an athlete.

Polar focuses on recovery and readiness metrics, which helps prevent overtraining. The company's approach to training load and recovery feels more conservative than Garmin's, which some runners appreciate.

COROS training tools have improved dramatically through software updates. If you have a COROS watch, you'll continuously experience new features being added, making your watch better and better. The training metrics now rival what Garmin offers, though the app interface remains less polished.

The Verdict: Which Watch Should You Buy?

For most marathon runners, the COROS Pace 4 at $249 represents the best value. You get accurate GPS, comprehensive training metrics, exceptional battery life, and a bright AMOLED display for half the cost of premium competitors. The limitations in smartwatch features and music streaming won't matter if you care primarily about training data.

If you want the most complete training ecosystem and don't mind spending more, the Garmin Forerunner 265 at a discounted price (often $100-150 off) brings a stunning AMOLED screen, multi-band GPS, and advanced training metrics to the masses. Garmin's extensive feature set and refined app make it the safe, comprehensive choice.

Polar deserves consideration if you prioritize heart rate accuracy and recovery insights above all else. The Polar Vantage M3 or Pacer Pro deliver professional-grade biosensing at reasonable prices, though you'll sacrifice some battery life and pay slightly more than equivalent COROS models.

The right watch depends on your priorities. COROS wins on value and battery life. Garmin offers the most complete package with the best ecosystem. Polar excels at recovery tracking and heart rate monitoring. All three will accurately track your miles and help you reach the marathon finish line.

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