I have been carrying out a spot of plant trials in my own garden. Trialling the more common and readily available Rudbeckia fulgida var. 'Goldsturm' with the less popular not so common Rudbeckia fulgida deamii.
Deamii wins !!!
I planted them in the same border, next to each other, therefore same aspect, soil and water availability
Goldsturm finished flowering 2 weeks ago, deamii still flowering and looking great, I also prefer the leaf on deamii. I know which Rudbeckia I'll be opting for in my next clients garden!