My opinion has kind of evolved on the starter bike thing. I used to be all aboot getting the low powered, old jap bike, but meow that the used market for starter bikes has went in the tank, you will have a hard time selling these things when you're ready to upgrade. So my opinion meow would be to find a neutral positioned (non clip on ) bike that you can grow into, and the monster fits that bill perfectly. Either one will work, but the added safety features of the 821 will benefit a new rider, especially the ABS. It makes no sense to me to say that the detuned riding mode wouldn't be safer, because that was the exact purpose it was put on for. Understandably, at the end of the day, the final judge is your right wrist, but as a newbie, those features still help.
I would go 821, then go to monsterparts.com for some frame and axle sliders, then get a good armored jacket, pants, and gloves. Then take a riders course, practice the hell out of panic breaking, and enjoy the shit out of your beautiful new bike. Hope this helps OP, welcome to the club.
Meow