A wrist slate is hard to pass off or set at a viewing angle for your buddy. If you use wrist gauges, then you don't have much room for a wrist slate.
The only time I've ever found a likable use for it was when I was leading refresher sessions or basic pool sessions. Held down notes very easily and at a quick glance.
My go to wrist slate was the 5-page, bungee held version (not the O-ring version). The bungee version held together in current and regular abuse much better. The O-ring version had to be repaired with new O-rings every so often, and it flapped open a lot.
After getting wrist gauges I moved onto a standard small slate and wetnotes. Depending on the dive I'd take one or the other. Both are stored in my pocket. IF I'm taking photos, I usually sport my slate, clipped off to a D-Ring, and use it as a white balance.