Of course, it all depends on how it is used.
We have an extensive collection! Many that he has made himself.
I have to say if all things equal (swung same way, same position, same force etc)
then a lexan paddle with holes has to sting the most.
After a few swats, the skin gets hot and sorta a moist feeling so that further swats "stick" a little before being pulled away.
After a good spanking with that, I have had all kinds of marks! many circle bruises or close to bruising that can last a few days.
STINGS like holey (get it :p) hell!
Edited: just asked boyfriend what he thought might be based on my reactions and he said he thinks it is definitely our RUBBER paddle and flogger.
This makes sense because the rubber "grabs hold" and pulls with each swat.
He may be right.
He has promised a "scientific" experiment tonight to determine.
I am actually curious now though I might regret it later tomorrow sitting during our traditional family Friday after Thanksgiving leftover lunch with the relatives !! lol