Feathers are at least a 12
Swedes are a very good 9.5
A new Sharp blade would be around 8
Derbys and Israelis I find equal at about a 6
And Merkur cruises along the bottom with a 4.
Hmmm... I am not a consistent DE user but there seems to be a liking for the less sharp of the above blades. Other threads I have seen indicate a preference for the Israeli blades and the Swedish Gillettes.
Steve