The major diffrence is in the number of input/outputs. When it comes to hdmi in/out rk+ has 3/2, rk pro has 6(5 hdmi, one sdi)/3. Audio rk+ has 3/1, rk pro has 8/3.
you can take a rk+, add a hdmi matrix, a DSP and a control system. Add to that the cost of configuring and programming the separete components. We have opted for the pro in a auditorium just to reduce the number of components.
What is best for one application depends on what is required.
