gistfile1.txt

require 'benchmark/ips'

class Foo
  define_method("foo") { }
  class_eval 'def bar; end'
end

Benchmark.ips do |x|
  foo = Foo.new
  x.report("class_eval") { foo.bar }
  x.report("define_method") { foo.foo }
end

          class_eval  6874955.4 (±1.0%) i/s -   34395821 in   5.003561s (cycle=205963)
       define_method  6187071.9 (±1.7%) i/s -   30989768 in   5.010413s (cycle=289624)