A BlackBerry android phone has the hardened OS - how that differs from the Samsung with Knox is for others to debate.
It also has built-in Dtek app - also debated often in how useful it is.
The OS UI is near stock, even with the launcher. However, like any android phone, you can install any other launcher you wish.
Basic BB app functions are the same. I don't think there are any real differences in the way, for example, the Hub functions no matter what device it's on.
I have an S8, and most of the BlackBerry apps, and I like the way they work better than the Samsung apps for emails, calendar and contacts.
I use Cobalt's BlackBerry Manager which bypasses the Google versions. This allows use of the BlackBerry virtual keyboard which I love on the S8.
I'm also using the Nova launcher with the TeslaUnread sub-app to give me numbered notification badges on app icons. The count is inaccurate with the Hub icon, but I can live with it. It correctly shows when something is there.
Not much of a difference.... on the device you get the keyboard app, and the DTEK app and some gestures that work better in the launcher.
A few have complained about the apps performance issues... even a few KEYone users that have removed it for other less resource intensive apps. Only you can really judge this, so suggest you give it a try.
My S7 I just have HUB and keyboard (can be found - thanks Cobalt), as there were issues with the default apps and the launcher isn't very good (IMHO).
I have an S8 and I use the Hub, Contacts, Calendar, Tasks and Password Keeper. all you really need is the Hub and Password Keeper. All the other BB stuff is BS.
Also, the reason I like the Hub is it shows sent and received emails together.
Lastly, the Samsung apps are not bad. Calendar and Contacts are very good.
I was paying the $1.00 a month for the BB Hub Suite and had a calendar issue. Deleted it and tried to reinstall and it said it was incompatible with my device. Then I deleted the whole Hub Suite and now I cannot install any BB thru the Google Play store. I started using Cobalt. I posted about it and nobody chimed in. The traffic on this site has really died down. 13 years with BB and now 3 months with Samsung, so far pretty happy.
I was paying the $1.00 a month for the BB Hub Suite and had a calendar issue. Deleted it and tried to reinstall and it said it was incompatible with my device. Then I deleted the whole Hub Suite and now I cannot install any BB thru the Google Play store. I started using Cobalt. I posted about it and nobody chimed in. The traffic on this site has really died down. 13 years with BB and now 3 months with Samsung, so far pretty happy.
Billions of people using Samsung and Apple, can't all be wrong.