benchmark.rb

require 'benchmark'

class PersonClass
  attr_accessor :name, :age
  def initialize(name, age)
    @name = name
    @age = age
  end
end

person = PersonClass.new("John", 30)
hash = { name: "John", age: 30 }

Benchmark.bmbm do |x|
  x.report("Class attribute access") do
    1_000_000.times do
      person.name
      person.age
    end
  end

  x.report("Hash key access") do
    1_000_000.times do
      hash[:name]
      hash[:age]
    end
  end
end

Ruby 3.2.2

With GC disabled:

Rehearsal ----------------------------------------------------------
Class attribute access   0.033338   0.000127   0.033465 (  0.033505)
Hash key access          0.036828   0.000000   0.036828 (  0.036859)
------------------------------------------------- total: 0.070293sec

                             user     system      total        real
Class attribute access   0.033789   0.000000   0.033789 (  0.033809)
Hash key access          0.036510   0.000000   0.036510 (  0.036533)

Without GC disabled:

Rehearsal ----------------------------------------------------------
Class attribute access   0.033027   0.000595   0.033622 (  0.033634)
Hash key access          0.037090   0.000000   0.037090 (  0.037102)
------------------------------------------------- total: 0.070712sec

                             user     system      total        real
Class attribute access   0.033549   0.000000   0.033549 (  0.033554)
Hash key access          0.036865   0.000000   0.036865 (  0.036885)