I got the Ionic for Christmas. I wanted this model since it is water resistant and I swim laps.
I also use it for the heart rate since I have Afib and it makes it nice to see if I have slipped into an episode. It is as accurate as my wrist BP and heart rate meter.
One minor drawback—When I mow the lawn, I get credit for bike riding rather than walking. It must sense my arms on the mower and mistakes that for handlebars.

Got the gf the alta about a year ago. She wears it for 2 reasons, one is its a watch, and 2, does the step challenge against her sister for fun. As for any other festures with it, uses it more for fun then for any real health reason since we are both active anyway. I know the only thing is she wishes it was waterproof since we are always swimming or on the boat during the summer. She ends up relying on ke for the time since my watch only tells time.