We have both...
For solo riding, The buddy (blackjack) is much easier to ride all the way around, I have been riding all sorts of motorcycles for 30 years, I sold a ktm 625 supermoto to buy my Blackjack.
The BJ is a solo ride but the wife and I have doubled on it fairly comfortable, Together we weigh 280.
The Stella is a beautifully made retro scoot with all the charm and quirks of the old world - manual shift - 2 stroke - squishy brakes, It is not much heavier than the Buddy but to me it felt off balance " heavy on the right side" The wife doesn't seem to notice
On the 2 mile brick road by our home the Stella smoothes out the ride much better than the buddy.
After riding both, I enjoy the Buddy for its simplicity and performance and the Stella for her charm... But she does have a steeper learning curve.
As far as foot room the Stella has more, I am use to riding sport bikes so I ride the buddy with my feet on the passenger plates in a tucked position...
Honestly, I am still not use to the riding position on a scooter, It just feels too... simple, I am use to my feet having a purpose- Braking/shifting, Doing nothing is just weird... but I would not change it for the world, Just love riding my scooter