Hall brand (Canada) farrier's crooked hoof knives are the hardest steel in my work shop.
Over the years I've used various steels for plane blades from whatever bog standard steel Stanley uses, Stanley Sweetheart laminated, O1, A2, through to Samurai Brand laminated, Mujingfang High Speed Steel, and Veritas powder metal PMV-11.
Ive even ground a two inch deep by 24 inch Agusta mechanical hacksaw blade to make a plane blade, can't say I'll be doing that again as it was fully hard and a bear to grind.
The Samurai Brand laminated is brilliant, as is the Veritas PMV-11. Holds a great edge and easy enough to sharpen with diamond hone.
Jury is still out on the Mujingfang HSS and the Agusta HSS blade because they only fit my No3 handplane which doesn't get much use and much of the jobs I've been on recently have been softwood and MDF type work.
When I get on a decent site that uses a lot of hardwood I'll be able to test them better.
I reckon the Agusta may well chip as its fully hard, the Mujingfang will perform well cos although its HSS its not as stupidly hard as that. Also there's a bloke who has tested the Mujungfang blades and has good numbers to back it up.
The Samurai and Veritas powder metal blades are a huge improvement over standard and O1. I prefer A2 to O1 but its not as clear cut as the difference is less.
You might note that all of these are carbon steels (a term I've never really liked as I don't feel it fully shows what other alloying elements in there) but thats just whats avalible for planes as almost all the time they get used on dry timber. Corrosion isn't so much of an issue apart from during long term storage.
Planes are a very good test bed for blade steels because they offer repeatable strokes, all held at exactly the same angle.
Do a load of strokes with one, same amount with another on the same block of wood then (if its not already obvious by the shavings) inspect the blade with a microscope.
Now I don't have a microscope so can't do that part but fortunately someone else has done that and put his results up on the internet. Yay.
Knife testing? Jeez, have you seen some of the stuff on Youtube? Using different length blades against each other, different angles, hacking all manner of stuff, lets cut a brick? Much of its a bit Wally Factor nine for me.
I'm afraid I've moved sideways from the general topic but thats conversations for yer.