class_vs_new.rb

require 'benchmark'
include Benchmark 

n = 500000
Benchmark.benchmark(CAPTION, 20, FORMAT, ">total:", ">avg:") do |x|
  x.report('via usual syntactics')  { n.times { class MyError < StandardError ; end && Object.send(:remove_const, 'MyError') } }
  x.report('via Class.new') { n.times { MyError = Class.new(StandardError) && Object.send(:remove_const, 'MyError') } }
end

# Results
#                            user     system      total        real
# via usual syntactics   0.125000   0.000000   0.125000 (  0.114111)
# via Class.new          1.046000   0.015000   1.061000 (  1.082029)
#
# => it seems it's an order of magnitude slower