Garmin Instinct 3 vs Apple Watch Ultra 3: Which GPS Watch Wins?

Overview

The Garmin Instinct 3 is a rugged endurance tool built for athletes who prioritize battery life and durability over smartwatch polish. The Apple Watch Ultra 3 is a premium device that blends top-tier GPS accuracy with a full smartphone companion experience, at a significantly higher price. These two watches share a target audience of serious outdoor athletes, but they solve different problems.

Specs at a glance

Price tier: Instinct 3 around £350-£450; Ultra 3 is premium flagship pricing
GPS: Both dual-frequency multi-constellation GNSS; Ultra 3 edges accuracy benchmarks in open water and urban conditions
Battery (GPS mode): Instinct 3 MIP Solar up to 48h with solar assist; Ultra 3 approximately 18h standard GPS, 72h low-power mode
Weight: Instinct 3 MIP at 48g; Ultra 3 at 61.4g
Display: Instinct 3 offers MIP solar (always-on, battery-efficient) or AMOLED; Ultra 3 uses always-on microLED with flat sapphire crystal
Sensors: Both include optical PPG heart rate, HRV, SpO2, barometric altimeter; skin temperature on Ultra 3 and Instinct 3 AMOLED only (absent on MIP variant)
Water resistance: Both rated 100m; Ultra 3 adds EN13319 dive certification
Maps: Ultra 3 includes onboard mapping; Instinct 3 does not

GPS and tracking accuracy

Both watches use dual-frequency multi-constellation GNSS and perform reliably in open terrain. The Ultra 3 pulls ahead in benchmark testing. In satellite acquisition and connectivity comparisons, it outperforms the Garmin Fenix 8, which sets a high bar. In open-water swim GPS accuracy, it beats the Forerunner 965 directly, a meaningful result for triathletes where wrist GPS during swimming is a known weakness across most watches.

The Instinct 3 tracks accurately in open terrain and holds well under tree cover and in urban canyons. It performs comparably to the Ultra 2 in standard conditions, but review data does not place it ahead of the Ultra 3 in any GPS accuracy category. The Instinct 3 also lacks onboard topographic maps, which is a real limitation for trail navigation compared to the Ultra 3 and several competitors at a similar price point.

Battery life

This is where the Instinct 3 MIP Solar wins decisively. Up to 48 hours in GPS mode with solar assist, 150 hours in expedition mode, and effectively unlimited smartwatch runtime in adequate sunlight. For multi-day fastpacking, ultra events, or anyone who forgets to charge, that is a practical advantage with no equivalent on the Ultra 3.

The Ultra 3 offers around 18 hours in standard GPS workout mode. That covers a Half Ironman with careful management. It does not cover a full Ironman or any ultra-endurance event without the 72-hour low-power mode, which reduces GPS fidelity. The Instinct 3 AMOLED variant closes the gap somewhat at around 30 hours GPS, but the MIP Solar version remains in a different category for endurance battery life.

For athletes: who wins?

Road running: Ultra 3. Superior GPS accuracy in benchmark testing and richer post-run data integration with Apple Health and third-party apps.
Trail running and navigation: Ultra 3 for onboard maps and GPS accuracy; Instinct 3 MIP Solar if multi-day battery life or solar charging matters more than turn-by-turn navigation.
Triathlon and open-water swimming: Ultra 3. Demonstrated open-water GPS accuracy advantage over leading Garmin swim trackers is a concrete win for this use case.
Ultra-endurance and expedition: Instinct 3 MIP Solar. 150-hour expedition mode and solar charging are unmatched here. The Ultra 3 cannot compete for events over 18 hours of continuous GPS use.

Verdict

For most athletes training across running, cycling, and swimming who want the most accurate GPS data and a watch that works seamlessly as a daily device, the Apple Watch Ultra 3 is the stronger choice. Its GPS accuracy leads benchmark testing, its open-water swim tracking is class-leading, and onboard maps add real trail utility.

The Instinct 3 MIP Solar earns its place for one specific profile: athletes who regularly push beyond 18 hours of continuous GPS use, operate in remote areas without charging access, or simply refuse to manage daily charging. No watch at any price beats it for battery endurance. Buy the Instinct 3 MIP Solar if you run ultras or do multi-day expeditions. Buy the Ultra 3 if you want the best GPS accuracy and a watch you can actually live in.