Heinrich. Regarding different OS's being difficult to use, they are all giving your different directions to get to the same place, once learnt...it's easy.
The 3K is the better board, but at twice the price (PA50) it should be. 3K Vocal Harmoniser is poor and distorts.
If I did not have the 3K I could happily live with the PA50.
I use both models stacked which gives me a combination of Yamaha & Korg Styles & Voices.

You have received some good replies above and it's really your choice of what you feel suits your needs.