gistfile1.txt

Desktop% ruby -v                                                              (~/Desktop)
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-linux]

Desktop% cat benchmark_quotes.rb                                              (~/Desktop)
require 'benchmark'
n = 1000000
Benchmark.bm do |x|
  x.report('assign single') { n.times do; c = 'a string'; end }
  x.report('assign double') { n.times do; c = "a string"; end }
  x.report('assign interp') { n.times do; c = "a string #{'b string'}"; end }
  x.report('concat single') { n.times do; 'a string ' + 'b string'; end }
  x.report('concat double') { n.times do; "a string " + "b string"; end }
end

Desktop% ruby -w benchmark_quotes.rb                                          (~/Desktop)
       user     system      total        real
assign single  0.270000   0.010000   0.280000 (  0.273250)
assign double  0.260000   0.000000   0.260000 (  0.264455)
assign interp  0.270000   0.000000   0.270000 (  0.265007)
concat single  0.630000   0.000000   0.630000 (  0.637348)
concat double  0.630000   0.010000   0.640000 (  0.634218)