Don't worry if you're not scaling K2 any time soon -- there are some universal upgrades as well. The Plus models pack the music, payments and maps you'd expect from Garmin's latest watches. That's more than a little handy for features like a round-trip creator that automatically generates routes for your next run or bike ride. They also include Galileo tracking to find your location when GPS alone might fail, and the more compact Fenix 5S Plus (shown at left) stuffs in a larger 1.2-inch screen while still remaining suitable for slimmer wrists.
Your choices mostly come down to battery life and case size. The sleeker 5S Plus lasts a week in smartwatch mode, or four hours in GPS and music mode. Step up to the slightly bulkier 5 Plus and you'll get 10 days of smartwatch use and 8 hours of GPS/music, while the chunky 5X Plus lasts for 20 days as a smartwatch and 13 hours with GPS/music.
Be prepared to pay a premium for this do-everything design, though. The Fenix 5 Plus range is even more expensive than the original with prices ranging from $700 to an eye-watering $1,150. You're getting one because you absolutely depend on accurate fitness tracking -- the smartwatch features are just a bonus.