Difference between spring steel and 65 Manganese Steel

Carbon content for spring steel and 65 Manganese Steel is the same 0.62~0.70%；Difference is that 65  Manganese Steel contains 0.9%-1.2% of Mn , while 65  Manganese Steel contains 0.50~0.80%  of Mn .
Hardenability for 65  Manganese Steel is better than spring steel . Raw spring steel is harder than  Manganese Steel , it is more diffiluct to machine . After heat treating , there should be no big difference between the two materials . 
Spring steel is more expensive than  Manganese Steel .