The Fenix 5X ($1,099, the version tested) is the flagship model of Garmin's new premium Fenix 5 series GPS running smartwatches. The other models are the 5S and 5 (both from $899 each).

The major difference among the three models lies in the size of their stainless steel case.

The 5S has a 42mm case, the 5 has a 47mm one, while the 5X features a 51mm case with sapphire crystal display only. You can choose between a sapphire and a non-sapphire model for both the 5S and 5.

Each Fenix 5 model uses a watch strap of different width (5S - 20mm, 5 - 22mm, 5X - 26mm). So you might want to double-check when buying replacement straps.

Garmin uses the new QuickFit straps for the Fenix 5 models. You just need to press a button to attach or detach the strap. It's really easy to use, compared with conventional straps.

I tried the default silicone strap and a metal one ($309) for this review with the 5X. Both are very comfortable, but the silicone strap makes more sense for running while the metal version makes it ideal for formal occasions.

The Fenix 5S has a slightly smaller 1.1-inch (218 x 218 pixels) round display, compared with the 1.2-inch round display (240 x 240 pixels) found in the 5 and 5X.

But the Fenix 5X is the only model that features pre-loaded maps that include those of cycling routes and even golf courses.

Because of the need to store maps, the 5X comes with 12GB of built-in storage, compared with 64MB of storage in the 5S and 5.

All the Fenix 5 models come with built-in Garmin Elevate wrist heart-rate technology for all-day heart-rate monitoring. Each model is water resistant down to 100m, so you can swim with it.

The watches are also all preloaded with multi-sport features such as running, hiking, swimming and biking, which is more than what most would need.

In addition, they come with a three-axis compass, a gyroscope, a barometer, an altimeter and - of course - GPS. They also double as a smartwatch that notifies you of social-media updates and incoming messages and calls when paired with a smartphone.

Design-wise, the Fenix 5S looks slightly different with a thinner bezel, while the 5 and 5X look alike with a thicker bezel. But all the models have three buttons on the left and two on the right.

They all look good enough for both the gym and the boardroom. You just need to change the strap for the latter.

The watch face displays the time and date by default. You can download and install new watch faces via the Garmin Connect Mobile app (iOS or Android).

Pressing the middle and bottom buttons on the left toggles to the digital compass, calendar, barometer, altimeter, thermometer, fitness tracking and notifications panels.

To get to the workout page, hit the top button on the right.

Use the middle and bottom buttons on the left side to scroll up or down to select the workout you want (you can now customise the workouts here). To start, press the top-right button again.

At the workout window, you can scroll to Map and see where you are. This is great if you are hiking and want to make sure you are on the right track.

But I think I have been spoiled by the more-intuitive touchscreen interface of other smartwatches. Thus, these button pressings are very counter-intuitive to me.

Despite having reviewed previous iterations of Fenix watches, I still find myself pressing the wrong buttons, like pressing the upper-left button to scroll up.

However, during workouts, the Fenix 5X performed without a hitch. On my first try, the GPS fix took more than 1min. But, subsequently, it was able to secure a GPS fix in around 10sec from the streets of my Housing Board estate.

Its distance tracking was spot-on, with a mere 10m difference when measuring my usual 5km running route. Daily steps tracked showed a difference of only 2 per cent, compared with my calibrated Apple Watch Nike+.

The Fenix 5X's heart-rate readings differed by around 4 beats per minute from those of my Polar H10 Bluetooth heart-rate monitor chest strap.

Battery life is superb. Connected to my iPhone 7 Plus as a smartwatch constantly with a run every three days, it lasted 10 days before needing a recharge.

Trevor Tan

•Verdict: Notwithstanding its slightly hefty price tag, the Garmin Fenix 5X is very much the perfect GPS running smartwatch to have if you are very much into multiple sports.