Comment by toast0

It's all tradeoffs. For my personal use, array performance would have to be terrible for me to notice, but durability is important. I've run systems at work where durability isn't required, but performance is.

If you run a fully matched array, you may well get better performance, but you also may wake up one day to all your disks disappeared. There's other ways for all your disks to disappear too, but same firmware, same firmware bug feels more preventable than power supply failed very hot.