The Sense 2 is a stress monitoring device. Whilst the Sense does give you a stress score it doesn't do all-day monitoring. The Sense 2 will also get Google Maps and Google Wallet (though who knows when that will be).
They seemed to have dropped a whole host of features from the Sense 2 including third party apps and clock faces so you won't be able to go to the app store and download things like Uber or even basic utilities like Calendar, you only get the handful of apps that Fitbit make and that also doesn't include Fitbit apps like the one that allows you to swap watch faces from the device itself, which now has to be done on the phone app again like in much older devices. It doesn't even support some premium features like Snore detection, like the previous model does.
If you aren't interested in monitoring your stress and being sent notifications to "check-in and reflect" (you pick from a short list of emotions - like 'calm', 'content', 'frustrated', 'happy' etc - to explain how you were feeling 15 minutes ago or whenever the change was detected) or this isn't enough of a feature to rule out the missing aforementioned features then I wouldn't bother keeping/buying it in the first place.
NB You can also compare features on their shop page, at the time of writing, it says the continual stress monitoring is the only thing that distinguishes the old from the new model (with Google Maps & Wallet coming soon) but as mentioned, there's a whole bunch of things they're not showing on that page, like third party apps and snore detection. The whole release has been a bit of a botch if you ask me.
