I guess it depends on what you are looking for. Unfortunately, Fitbit has switched almost entirely to wrist models, so if you want a clip-on like their wonderful One ... they no longer offer that. If you want something slim, the flex2 (no display though, you have to check the app to see your numbers) or Alta (comes with or without heart rate option for a price difference). I personally LOVE having the heart rate feedback. All the other upper models have HR and floors (which the Flex and Alta do not have). Some models offer GPS, I'm not really familiar with the newest options ... looks a lot like an Apple Watch. Fitbit has a pretty good breakdown of all the models and their options, so you just have to determine which features you want and how much you are willing to pay.