In my experience, flash drives are way more reliable than SD cards and I'd put SSD and HDD above both of those.
I wish they'd just ditch the SD card on the Pi already as it's always the most likely reason why your stuff stops working. For my Pi running Home Assistant, I've swapped to an SDD as the boot drive. For the others, I still use SD cards but they're just doing basic stuff like running Klipper on my 3d printer or a (WIP) live photo frame that can be easily swapped with a replacement SD later.