Lindsay,
I upgraded to a Fenix Fs which now has 3-4 days of battery life after adjusting a few settings that Garmin happily helped me with. It integrates with the TrainingPeaks platform seamlessly, the altimeter is easy to calibrate, works with a HR chest strap, tracks steps, sleep quality and is pretty user friendly for a techy watch. Being small, the size of the watch was important to me. I’ve worn clunky altimeters for years. Although the Fenix 5s is not tiny, it’s super reasonable for small wrists. It is pricey but considering the level of support you get from Garmin, it’s battery life and integration with TP I’m super happy with it.