I can give quite a good impression/review of these as about a year ago I fitted two RF cinch cranks (one Turbine and one Aeffect) to 2 bikes within weeks of each other.
The Turbine came with an Alu cinch ring, and the Aeffect was cranks only so I bought a steel RF ring. Both bikes ridden about the same distance in that time (about 1000 miles apiece).
The steel ring is showing a lot less wear than the alu one, but both are currently still going strong, with no chain drop evident in either yet.
By eye I’d give the alu ring another summer and winter of riding.
The steel ring on the other hand looks hardly worn, apart from paint loss on the teeth.
It does show a little rust if left after a wet ride (not a problem right now!) But a quick spray with lube and it’s fine.