require 'benchmark/ips'

Benchmark.ips do |x|
  x.report("Kernel") { Hash(nil) }
  x.report("Hash")  { Hash.new(nil) }
end

# Warming up --------------------------------------
#               Kernel   307.226k i/100ms
#                 Hash   117.067k i/100ms
# Calculating -------------------------------------
#               Kernel      9.192M (± 5.7%) i/s -     46.084M in   5.029888s
#                 Hash      1.729M (± 7.8%) i/s -      8.663M in   5.039179s