Map is incredibly slow. Of course it's a little bit weird to let Ruby run 10M loop.

bm_map_vs_push.rb

require 'benchmark'

MAX = 10_000_000

Benchmark.bm(3) do |b|
  b.report("push") do
    arr = []
    MAX.times {|i| arr.push(i.to_s)}
  end

  b.report("map") do
    arr = (0...MAX).map(&:to_s)                                                                    
  end
end

result.txt

         user     system      total        real
push 24.460000   1.880000  26.340000 ( 26.850189)
map  36.910000   0.910000  37.820000 ( 39.286317)