Ruby array += vs <<

shell.log

$ ruby test.rb 
40.268058
0.046918

test.rb

interactions = 100_000

a = Time.now
contents = []
interactions.times do |i|
  contents += [i.to_s, i.to_s]
end
puts Time.now - a

a = Time.now
contents = []
interactions.times do |i|
  contents << i.to_s
  contents << i.to_s
end
puts Time.now - a