In my opinion, (and everyone has one, YMMV) I have 3 favorites< I know strange but true.
-Feather in my slant, (black right now because thats what I have)
-Iridium in my Chatsworth
-IP in my Futur
The Feather I feel is the sharpest of the 3 followed by the Iridium and the not nearly as sharp but great shaving IP.
For me just because a blade is real sharp doesn't make it the best. Unfortunately 2 of the 3 blades that make me say WOW are more expensive than most. There are many other blades I like and use on occasion:
7 O'Clock yellow
Kia
Bic
Astra
Sharp
Red Pack Persona
As far as longevity I really couldn't say because I typically change on the 3rd shave
There cheap enough, why risk it?