Funny you would say that about Astra SP. Those have been my go to for years in a row and never did I have a bad blade.I haven't tested so many blades yet. I started with DE razor this year.
The razors I use is a Futur clone and a Yaqi top aggressive.
Gillette Perma-Sharp, always a good blade.
Bluebird (Derby), sharp but not as smooth as PermaSharp.
Wizamet, almost as good as PermaSharp but sometimes a dull blade.
Treet Platinum, good and always the same, this is my main blade.
Asco SS. Very good. Not the sharpest but very smooth.
Astra SP, similar to Treet Platinum, but too often a dull blade will be there.
Blade that disappointed me,
Suneko, read a lot of positive things that I never experienced.
Derby Extra, Bad QC. They are average to bad blades for me.
Lucky to say most of the 100 packs I have were bought in quick succession back in the day and are all produced within the same year.