SR77 is what they use for jack Hammer bits, it's an impact steel so is perfect for large choppers and axe type tools. During impact with hard objects such as an unseen nail in some wood the SR77 would usually roll/deform whereas SR101 ( Ball bearing steel) could possibly chip.....I only said possibly because with the Busse-Kin heat treat SR101 is amazing stuff !

SR101 is definitely the better at edge holding out of the two steels, although once again due to the Busse-Kin heat treat I was quite suprised at the SR77's edge holding.

To some up in my view anything under a 8" blade would be better made of SR101. Anything over 8" and I'd sooner take SR77.